Graham Potter described Chelsea's performance as "not good enough" after a 1-1 draw at Nottingham Forest – as Jimmy Floyd Hasselbaink warned the Blues face Champions League misery.
Hasselbaink believes his former club are destined to miss out on a top-four finish after they slipped up at the City Ground on New Year's Day.
Chelsea won the Champions League only two seasons ago, and head coach Potter may find himself under pressure if they are not playing in Europe's premier club competition in the 2023-24 campaign.
The London club are eighth in the Premier League, seven points behind fourth-placed Manchester United.
Ex-Blues striker Hasselbaink told Sky Sports: "I think they are too far from the top four. Yes, they do miss some really important players – [Reece] James, [N'Golo] Kante, [Ben] Chilwell – but they are defensive-orientated players.
"He [Potter] needs to win matches, he needs to win as many matches as possible. Chelsea need to be in the Champions League. That's not going to happen.
"He's had a lot of injuries and you need to give him time. You need to give him time to mould his team."
Potter saw Chelsea squander an early lead on Sunday, with Raheem Sterling's strike countered by a fine second-half reply from Serge Aurier.
Former Brighton and Hove Albion boss Potter described it as "a hard-earned point against a team that's set up well", and he praised the spirit in the Forest ranks that saw them raise the tempo after half-time.
But that may not wash with the Chelsea supporters who expect their team to be able to ride out such pressure against teams battling to avoid relegation.
Forest, who are 18th in the table, could easily have secured all three points, as they had the better chances in a lively game.
Chelsea have won just one of their last seven Premier League games, losing three and drawing three in that run.
"Our performance level wasn't good enough, I don't think, to take the three points," Potter said.
"When we had control of the game we didn't move the ball fast enough, there wasn't enough movement for us, and when we lost control of the game we struggled a bit."
Potter said it "would have been unfair" if Pierre-Emerick Aubameyang had converted a late chance. As it happened, the striker failed to get his head on a cross from Hakim Ziyech.
The Chelsea boss said his side "didn't deserve to win the game with that", and he refused to discuss possible new signings, amid claims defender Benoit Badiashile is poised to sign from Monaco.
Asked about Champions League qualification, Potter said: "We've got a long way to go in terms of how we want the team to look and the performance level. It would be a mistake for us to worry about what can happen in five months' time.
"We need to focus on the next match and get our performance level better and more consistent."
The next match is a Premier League home game against reigning champions Manchester City on Thursday, and the game after that is another clash with City on Sunday in the FA Cup third round.
It gets no easier for Potter who said his team's midweek win against Bournemouth had been "a step forward".
"Today was a little bit of a backwards one," he added.