Jose Mourinho has no intention of repeating a mistake from the past and will "go serious" when Manchester United go to Blackburn Rovers in the fifth round of the FA Cup on Sunday.

United are the only side in England still challenging on four fronts - in addition to the FA Cup, they face Southampton in the EFL Cup final next weekend, overcame Saint-Etienne in the first leg of their last-32 Europa League tie on Thursday and continue to challenge for a top-four spot in the Premier League.

It has left Mourinho with a fixture pile-up to contend with, but the Portuguese insists he will still field a strong side at Ewood Park to avoid a mistake similar to the one he made in 2005 during his time at Chelsea, when his side lost 1-0 at Newcastle United.

"I threw it away [in 2005]," he said.

"In the same week there was the Champions League game against Barcelona and the League Cup final against Liverpool, and in the middle of that was the FA Cup game against Newcastle.

"I threw it away, gambled too much and focused on Barcelona and Liverpool.

"It was good because we beat Barcelona and won the final against Liverpool, but the feeling of throwing it away was not good so I won't throw it away.

"If I lose, I lose because the opponent was better or that we didn't play well but I am not going to throw it away and go to Blackburn with that respect.

"We have played Reading and Wigan from the Championship so the level and difficulty of the Championship is not new for us. Plus it is one thing to play at Old Trafford but it is another thing to go away. So I go serious.

"Am I going to repeat this team [he played against Saint-Etienne]? No. I am going to change a few players obviously, but I am going with a good team because I respect the competition a lot and Manchester United demands you go serious into every game."

Mourinho made amends at Stamford Bridge by claiming the trophy in 2007 and he is targeting another Wembley success 10 years later after outlining his respect for the competition.

"Maybe we don't have as many English managers with that culture [of respecting the FA Cup] as we should and maybe we as foreign managers, not everybody studies and understands the culture of this country," he added.

"In the first time in it I had immediately the situation with the match at Newcastle and for me it was a lesson and I lost with Chelsea against a League One or League Two team [Bradford City] but I never threw it away.

"I always like to go serious, I like Wembley and I like the FA Cup so I have to try to get my second one."

Wayne Rooney and Michael Carrick missed the Saint-Etienne game through injury and are unlikely to be fit for the short trip across Lancashire, but Henrikh Mkhitaryan may be available.

On Rooney and Carrick, Mourinho said: "I want them to be fit and ready because even on Thursday if they were they would be involved. I need every player to choose from but I am not sure they will be ready because the game is in three days.

"Henrikh is ill and stayed at home.

"On Wednesday he was feeling a little bit better and the doctors were on it and hoping he would be ready but he was not, so let's see."