Everton face seven days that will define the rest of the season after a bittersweet weekend that changed the club’s outlook on multiple fronts. The hard-fought win over Brighton & Hove Albion pushed the Blues seven points clear of trouble and cemented the surge in confidence that has followed the return of David Moyes.

But injuries to key players Dominic Calvert-Lewin and Orel Mangala cast a shadow over the valuable win. Both players face full assessments but fears their injuries were serious were clear after the final whistle at the Amex Stadium.

The setbacks threaten to hamper the Blues in two areas where reinforcements were already considered desirable heading into the final week of the transfer window.

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They will also undermine preparations for what will be the pivotal visit of Leicester City on Saturday. The Foxes’ surprise win at Tottenham Hotspur on Sunday revitalised a stalling survival bid and added fresh significance to a match that, should Everton win, would allow the club to open up a chasm to the bottom three.

Dominic Calvert-Lewin lasted for just 12 minutes at Brighton when the forward pulled up with a hamstring injury suffered as he challenged for a long ball. The concern was immediately apparent, with the 27-year-old clearly in discomfort as he flagged the attention of medical staff in the nearby dugout.

While he stressed the need to await a full assessment of the severity of the injury, after the game Moyes did not hide the worry that it could be a troubling one.

There was similar concern over Mangala, who picked up a knee issue in a clash with Joel Veltman in the second half. The midfielder, who has grown into an important player since his arrival from Lyon, returned to the pitch after receiving treatment and quickly collapsed in pain before hobbling down the tunnel.

Moyes said: “They don't look great, either of them, but the medical team have told me to let you know they'll get assessed first and then we'll make a decision. But I think they seem to think they're not the best, either of them, at the moment.”

The Blues boss went further with Mangala, returning to the issue later in the post-match press conference to add: “I've got to say, Mangala's got a bad injury as well. So, we've had a difficult day and if we had actually come away and not got a result, it would have felt much sorer because of the couple of injuries we've picked up. So, that was great credit to the players, their effort and commitment to get a result under the circumstances.”

The loss of Mangala for any length of time would be of concern to Everton. The 26-year-old has formed an effective partnership with Idrissa Gueye and played 19 times in the Premier League. His arrival late in the summer window was central to the Blues improving on a start that saw them lose their first four league games.

Mangala’s injury would partly be counteracted by the return of James Garner, who came off the bench at Brighton for his first appearance since suffering a back injury in October. Everton had hoped he would be able to play for the Under-21s to build up his fitness but injuries made it necessary to turn to him on Saturday afternoon. Though less experienced, and better suited further forward, fellow central midfielder Tim Iroegbunam is also on the cusp of a return to fitness after he, like Garner, picked up a serious injury in the October international break.

Even with the return of Garner and Iroegbunam, Moyes was hoping to strengthen in the middle during this transfer window and Mangala’s injury may add further weight to a push for Chelsea midfielder Kiernan Dewsbury-Hall.

The Blues are in talks with Stamford Bridge chiefs over the deal that saw Armando Broja move to Merseyside on loan in the final hours of the summer transfer window. The 23-year-old, who was just starting to gather momentum after overcoming an Achilles injury, was stretchered off during the FA Cup win over Peterborough United earlier in January and faces months out.

In order to return Broja to his parent club, and thus free-up a domestic loan slot, Everton need to reach an agreement with Chelsea and have countenanced taking Dewsbury-Hall or winger Carney Chukwuemeka in the hope it could lead to a breakthrough in negotiations.

While Dewsbury-Hall is the Blues' radar there is an expectation that any decision to sanction his departure from Chelsea would not be made until the later stages of the window, increasing concerns that holding out for him contains the risk that any plans fall through too late in the window to seek an alternative option. Before the weekend, Everton’s search had not led to the club embarking on a serious pursuit of Dan Neil of Sunderland, another central midfielder who has been linked this month.

Targets in that position could now be re-assessed, with adding to the midfield more important following the injury suffered by Mangala. But the situation further up the pitch is also a real priority.

The Blues have struggled for goals all season and have been seeking a solution for some time. While Moyes was open to exploring the market for forwards, the growth in confidence surrounding Calvert-Lewin that was bolstered by his goal against Spurs, combined with the constraints to Everton due to financial regulations and the consensus there are few reliable options currently available, meant attention was being directed towards how the England international could be better supported rather than on competition for him.

The need for wide players has been further exacerbated by the knee injury suffered by Dwight McNeil, who is also due to be absent for the near future.

Moyes conceded after Brighton, however, that the injuries - if as bad as initially feared - would impact the club’s approach to the closing stages of the window. He said: “I feel as if, depending on what comes back from their assessment, I'll decide a little bit more to whether we're having to go and do something, which we may have to do from what we've seen.”

Concern over the condition of Calvert-Lewin, whose contract expires in the summer, is set against an already troubling backdrop. Broja is set for an extended period on the sidelines, as is Youssef Chermiti, who is out for “weeks” with a thigh injury and who has not kicked a ball for the senior team this season.

Even in the event of his recovery, Chermiti has not scored a first team goal for Everton and so relying on him to make an impact on his return would be a gamble. That leaves Beto, who fought hard after replacing Calvert-Lewin on Saturday but has so far struggled since his arrival from Udinese 18 months ago - albeit his opportunities have been limited.

The Blues have already been linked to a number of forward players this month, with speculation over interest in Sporting’s Marcus Edwards and Monaco’s Breel Embolo already dismissed. Another forward whose name has cropped up is Evan Ferguson of Brighton.

His manager Fabian Herzeler said he was not part of the squad that faced Everton at the weekend because he was injured. Asked whether there was a chance he could leave the club on loan this month, Herzeler added: “I can’t say anything about that because I don’t know it.”

Ferguson emerged as a major talent two seasons ago but his progress has been undermined by injury setbacks. For Everton, his fitness would be one concern but another hurdle to any deal would be that the Blues cannot take a player on loan from another English club while Broja and Jack Harrison, who is with the club from Leeds United, remain at Finch Farm.

On Ferguson’s current mood, Hurzeler added: “When I see him he is in good spirits but of course injuries don’t help your mood and your shape, so not only physically but also mentally it is a tough time for him but I am sure he will get through it.”

In terms of a potential permanent move for Ferguson, the ECHO understands that despite the increased spending power going forward thanks to the takeover by The Friedkin Group (TFG), the club don’t have the finances to prepare a package of that magnitude in this window due to Profit and Sustainability Rules constraints, making a deal of any type highly unlikely at this stage.

Moyes is playing a significant role in the search for reinforcements and, with director of football Kevin Thelwell, has not come under pressure from new owners TFG to adopt a particular strategy.

There is an acknowledgement the club is caught between shifting circumstances, however, and a desire to avoid moves that could undermine the squad rebuild set to take place in the summer.

While there is money available to spend right now, the summer will be the watershed moment from which Everton escape the final restraints of PSR and the point at which TFG can dip into their resources to fund a genuine squad overhaul - one that will be helped by the swathe of players set to leave when their contracts expire at the end of this campaign.

Moyes believes players with experience and who can strengthen the dressing room are needed in the short term, but does not want to hinder efforts to develop the squad more progressively in the summer, at which point there is likely to be greater focus on youth and the development of younger players.

Despite that challenge, heading into the weekend there was cause for positivity around the work the Blues had done in the transfer window. While no incomings had been secured, there was a sense the groundwork had been done and that the club was in a good position to act on that in the closing stages of the window.

One player Everton had been looking at is Lyon winger Ernest Nuamah and he remained on the club’s radar as it continued to assess the market. It is unclear whether his goal on Sunday, his first of the season, will change Lyon’s stance on the 21-year-old but while he remains a potential target, the need for Moyes to be given players who can make an immediate impact has now grown stronger following the concerns over first team regulars Calvert-Lewin and Mangala.

There is a belief Nuamah could make an immediate impression but the events of the weekend have increased pressure on the club’s recruitment staff to find affordable players they can be confident will help the short-term goal of ensuring Everton remain a Premier League club.

A win over Leicester would represent another major step towards that goal but there is a determination at the club not to leave anything to chance. That much was clear even in the immediate aftermath of the win over Brighton, when senior staff were keen to stress the importance of remaining grounded and focused on survival.