Manchester United’s hopes of defending the FA Cup were dealt a severe blow after Wayne Rooney, Marcus Rashford and Anthony Martial were all ruled out on the eve of Monday night’s quarter-final against Chelsea.

With Zlatan Ibrahimovic starting a three-match suspension it means José Mourinho is without all of his frontline strikers for the trip to Stamford Bridge. The manager had planned to field one of Rooney, Rashford and Martial at No9 in the absence of Ibrahimovic. But with Rooney injuring himself in an training accident with Phil Jones on Sunday, Rashford falling ill on the same day and Martial also suffering an unspecified problem Mourinho will now have to field a makeshift forward line at his former club.

This may feature Henrikh Mkhitaryan as the most advanced player with Jesse Lingard, Paul Pogba and Juan Mata making up the remainder of the attack.

As United are fighting for a Champions League berth via a top-four finish in the Premier League or by claiming the Europa League Mourinho identified the Cup as the least important of the three competitions United are still in contention for.

But with their Europa League last-16 tie with Rostov poised at 1-1 for Thursday’s second leg at Old Trafford the concern will be if none of the Rooney, Rashford or Martial can recover in time. Ibrahimovic will be available as his suspension is domestic only.

Mourinho said: ”For me Chelsea is just a game that comes in the wrong moment for us, because the Europa League is a competition that can give us a Champions League spot, and the FA Cup, it isn’t so the Europa League is more important than the FA Cup for us.”

Mourinho also dismissed Antonio Conte’s criticism that he is to blame for Chelsea not playing in Europe this season by stating this cleared the way for their title challenge.

Mourinho takes United to the west London club having lost October’s league fixture there 4-0. He was previously in charge of Chelsea before being sacked in December 2015, his defending champions going on to finish in a disappointing 10th position last May.

Under Conte Chelsea have a lead of 10 points with only 11 games remaining. This means the Italian is on target to emulate Mourinho, who claimed the title in his debut season in English football – 2004-5 – during his first Chelsea tenure.

Last month Conte said: “We have this situation because of last season, not because someone invented it. Last season was very bad.”

When asked how hard it is to lead a side to the title in a first campaign, Mourinho pointed to these comments. “The most difficult thing to have is time to work and they have time to work,” he said.

“I know that Conte told a couple of days ago or a couple of weeks ago that it’s not his fault that they are not in the European competitions, it’s my fault and the players’ fault. But the reality is that he got in his hands a situation where they have time to work, time to rest, time to relax, time to disconnect, time to travel, time to have holidays, time to go to America [Thibaut Courtois] and enjoy America for a couple of days.

“They have time for all of these things, so they are in a position of privilege, the same privilege that Liverpool had a couple of years ago and they almost won the Premier League [2013-14]. But I don’t want to say that they don’t deserve credit for it. They choose a certain style of play that is very adapted to the qualities of these players, they defend a lot and well, and they counter attack and kill opponents on the counter attack similar to my Chelsea.

“The difference is they play with five at the back and I played four at the back, but the same criteria, a very strong team to defend and a team that kills on the counter attack, and they are doing very well and that is why they are going to be champions easily.”

Since that defeat at Chelsea United are unbeaten in the league and have lost only twice in all competitions – these reverses coming in the Europa League and EFL Cup semi-final second leg.

Mourinho said: “It is one defeat in so many matches and it is one defeat that you can allow because it’s the defeat that gets you into the [EFL] final so when we were losing that match against Hull [City], we did not need to fight [for an equaliser], we just needed to fight to keep in the tie to get into the final, and with that defeat we got into the final so I do not consider it as a defeat.”

Despite this form United remain in sixth place, 17 points behind Chelsea after playing a match less.

“They [players] are doing really well and, if we could change three or four draws at home in the Premier League for wins, it would mean we would have six or eight more points in the Premier League and we would be in a magnificent position,” the manager said. “So the boys are doing really well.”