The Catalans could have scored more in a decent first-half showing, but dipped dramatically after the break and will have been happy to hear the whistle as the home side pushed for an equaliser.
"In the end, we were tired," Setien admitted afterwards. "They put on players in attack and caused us problems."
Barcelona's small and ageing squad is struggling
When Barcelona fielded a front six against Sevilla last month which included five players over the age of 30 (plus a 29-year-old), coach Quique Setien said he was unconcerned because older players read the game better than youngsters.
Setien has also brushed off questions about Barcelona's small squad, but after nine matches in a period of less than a month, it is clear that the intense schedule is taking its toll .
Barca were missing Ansu Fati through suspension on Saturday, as well as Frenkie de Jong, Arthur and Samuel Umtiti (all injured), while Ousmane Dembele is still sidelined with a long-term problem and is ineligible for LaLiga anyway.
That meant Barca had just seven substitutes (12 are allowed post-pandemic) and only five outfield players on the bench. Poor planning has left the squad short and ill-equipped – especially for this current format.
Lionel Messi, Luis Suarez, Gerard Pique, Arturo Vidal, Ivan Rakitic, Jordi Alba, Sergio Busquets are all in their 30s, while Anttoine Griezmann is 29.
This team is running on empty and a break before the Champions League resumes will be much needed.
Messi sets another record, but he needs a break
Lionel Messi won the ball back and played the pass which set up Arturo Vidal for the winner in Valladolid to reach a career-best 20 assists in LaLiga, which levels Xavi's total from the 2008-09 campaign.
But the Argentine has netted just once in the last seven matches – a penalty in the 2-2 draw at home to Atletico Madrid – and even he is looking tired.
Coach Quique Setien said last month that Messi could conserve his energy during games, but he is the only Barca player to feature for every minute since the restart and the 33-year-old's form has suffered amid a punishing schedule.
Asked if Messi needed to rest, Setien said: "Surely. I mentioned it to him. But the scoreline was tight."
Fitness worry for Griezmann as Suarez slumps
Antoine Griezmann was rewarded for two good performances against Villarreal and Espanyol with a starting spot in Valladolid as Luis Suarez was surprisingly benched by Quique Setien.
The French forward took up good positions in the first half, but dallied on one occasion, completely mishit a shot on another and then did not reappear after the break as he was replaced by the Uruguayan.
It appeared harsh on the former Atletico attacker and in his place, Suarez offered very little. With his team-mates tired, the South American was something of a burden in a slow side on one of his forgettable evenings.
"He asked for the change because he had some discomfort," Setien said of Griezmann, who must now be doubtful for the remaining two games.
And on Suarez, the coach added: "He had to rest at some point."
Ter Stegen keeps Barca in the race
When Barcelona were on the back foot in the second half, Marc-Andre ter Stegen stood firm and the German goalkeeper made a number of vital interventions to keep his team in the title race.
After a first half in which he was barely called into action, apart from once to gratefully claim the ball when Kike Perez fell over as he was about to shoot from close range, the 28-year-old kept out two headers from Enes Unal after the break.
He also saved from Sandro in stoppage time and dealt with several dangerous crosses into the box as the home side sought an equaliser.
"Ter Stegen is there to make saves and that's what he is doing," Setien said afterwards in a matter-of-fact way. it was hardly the praise his goalkeeper deserved.
Barca need major Madrid slip-up now
Barcelona's win in Valladolid means Real Madrid cannot be crowned champions on Monday and it also sees Los Blancos' lead cut to a sole point, although Zinedine Zidane's side have a game in hand.
It is not over yet, but for Barca to claim the title for a third season in a row and a ninth time in 12 years, a major slip-up is now needed from their rivals and that seems improbable.
Since the restart, Madrid have won eight consecutive games and Zidane's side have not even a conceded a goal in their last five.
Barca need Real to lose one and draw another in their final three fixtures (against Granada, Villarreal and Leganes), while Setien's side have to win their remaining two games (versus Osasuna and Alaves). It is unlikely.