MIAMI -- Ander Herrera has leapt to Jose Mourinho's defence by insisting the Manchester United manager's frustrations during a turbulent preseason are justified.
Mourinho has had to contend with post-World Cup holidays, a lengthening injury list and difficulties in the transfer market while on the five-game trip in the United States.
His squad has become so stretched that just five senior outfield players -- Alexis Sanchez, Juan Mata, Luke Shaw, Fred and Matteo Darmian -- were able to train at Barry University on Monday morning.
The Portuguese coach has cut a frustrated figure but Herrera insists he understands his manager's concerns.
"I agree with him because it must be difficult for him to work with a group of players that maybe he is going to have 50 percent of them in the future," the midfielder said. "You cannot really work tactically because you would think the guys that are working could be leaving or going on loan or they are going to the second team, so it's difficult for him.
"It's also difficult for us but we knew in advance before coming that it was going to be like this.
"This is my fifth preseason and it's the most strange preseason here so far. The most important thing is to get minutes and be ready for the game against Leicester. That's all that matters."
Mourinho has nine days to prepare for Leicester's visit to Old Trafford on Aug. 10 but, after a turbulent tour, the 55-year-old has already concluded his team are "in trouble".
He has received criticism from some fans for not attempting to put a more positive spin on the new campaign, but Herrera insists Mourinho has shown a different side to players.
"I haven't watched the manager's media stuff, I never do," he added. "I cannot talk about how he is with you guys because I never see that. I can say that, with us, he is very positive. He wants us to fight for the titles, he wants us to perform to our best, he wants us to work as hard as possible.
"Probably, he's not frustrated about the club or the market, he's probably frustrated because he's not able to work with the players that he's going to have for the season.
"Other teams they are able to do that. For example, we played against Liverpool and they had maybe 80 percent of their squad ready, Milan maybe 90 percent of their squad.
"We have the situation with Matteo Darmian, he's playing now every game but probably he's going to leave, and then some kids, they're probably going on loan.
"I can understand the manager and if I put myself in his position, I would be in the same situation. You want to fight for the titles but you don't have the team with you to work for it right now."
After finishing second -- but 19 points behind the champions -- in the Premier League, there is pressure on United to challenge Manchester City this season.
Mourinho is still hoping to add at least one more player to his squad to help him do it but Herrera is adamant he already has the personnel to give Pep Guardiola's side a run for their money.
"My work is on the pitch, not in the office, so the only thing I can do is give my best and try to help Fred, Diogo Dalot and Lee Grant adapt as quickly as possible," Herrera said. "The other things, they are too far from my hands. So, I think we have fantastic players, but of course, always the managers want to improve their teams, but it's not my business.
"It's something between the manager and the club. From my position, the only thing I can give is my best in every training session and every game.
"I told you guys the other day in the media that I don't think we have worse players than any other team in the league, that's first of all. So we have to push ourselves and obligate ourselves to fight for titles."
United face Real Madrid on Aug.1 before travelling to the Allianz Arena for their final preseason friendly against Bayern Munich four days later.
On Friday Aug. 10, they open their Premier League campaign with a home clash against Leicester.