BOURNEMOUTH, England -- Manchester United manager Jose Mourinho is sweating on the fitness of Romelu Lukaku ahead of trips to Juventus and Manchester City.

The Belgian was not part of the United team that won 2-1 at Bournemouth on Saturday after picking up an muscle injury in training on Friday.

He will be assessed on Sunday before a decision is made about whether to include him the squad which flies to Turin on Tuesday.

"I have to wait until Monday," Mourinho told a news conference at the Vitality Stadium.

"He needs these couple of days. It was something in training. We don't know -- a muscle problem -- and we have to wait a little bit."

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In Lukaku's absence, Marcus Rashford, who turned 21 on Wednesday, came off the bench to score a stoppage time winner against Bournemouth.

Mourinho admitted his team were "lucky" to go in at half-time at 1-1 after Anthony Martial had cancelled out Callum Wilson's opener after what he described as some "absolutely awful" defending in the first half.

"The team looked like we don't work tactically during the week which is obviously the worst feeling for me because we work so much and I expect my team to be really good and I feel really frustrated with that," Mourinho said.

"The good thing is the team has the face of a fantastic character and the heart that the game is not over and we go until the end.

"In the first half we were a very, very lucky team. A first half that could should be game over 5-2, 6-2, easily, and in the second-half until we scored I was feeling we were a very unlucky team because in second half we should score three, four or five goals and we didn't so is what we traditionally call a game of two halves.

"In the first half Bournemouth was the best team by far and in the second half United were the best team by far."

Romelu Lukaku has not scored a goal for Manchester United since September. Getty

United's defensive problems were exposed again by Bournemouth, particularly in the first 45 minutes. Mourinho's team have kept just one clean sheet in their first 11 league games this season compared to eight over the same spell last term and the United manager believes it is the cost of playing more attacking football.

"The approach [last season] was much more defensive and with a much more defensive approach you can hide better your weaknesses," Mourinho said.

"So when the team is really defensive and you have a more defensive mind then you base the work on that then the team doesn't develop enough in other areas but the team managed to get results based on that. I'm trying to find a balance."