Another woeful performance in a 2-0 home defeat by Malaga on Sunday left them mired in 13th place in La Liga and the King's Cup is their only realistic chance of domestic silverware this season.
Their semi-final first-leg at home to Racing Santander on Thursday is also an opportunity to ease some of the pressure on coach Quique Sanchez Flores.
"Some team mates played nine matches in January and maybe they are tired," Ujfalusi told a news conference.
"We were very bad against Malaga and that's happened to us several times this season," he added. "I don't know the reasons for this slump and we understand that the fans are angry."
Forlan told Spanish radio: "We are playing a lot of matches in succession and the squad is not very large. We are feeling a bit tired."
Atletico president Enrique Cerezo has backed Sanchez Flores, appointed to replace Abel Resino at the end of October, but has warned that if the team's form did not pick up the club could be looking for a new coach.
"I believe he will be in charge of the team in the Cup final (in May), if we get there," Cerezo was quoted as saying in Tuesday's edition of Marca sports daily.
"His position is assured and both the players and club officials are happy with him," he added.
"But one thing is clear, as with all coaches, that if you don't win matches you have problems. They live by the results."
Sevilla, who knocked out holders Barcelona over two legs at the last-16 stage, scored an impressive 2-1 home win over Valencia on Sunday to revive their league campaign and host Getafe, whom they beat in the 2007 final, on Wednesday.
Scoring at least one away goal was the priority ahead of next week's second leg in Madrid, according to Getafe defender Miguel Torres.
"Sevilla have a great squad so let's see which team they put out on Wednesday," he told a news conference.
"At this stage of the competition it's hard to say if there are favourites."
