Manchester United defender Phil Jones has ankle injury - Jose Mourinho

MANCHESTER -- Jose Mourinho has questioned whether Manchester United can continue their impressive form once campaigns in the Champions League and League Cup begin after the international break.

Mourinho has also revealed he is sweating on Phil Jones' fitness after the defender picked up an ankle injury.

United sit top of the Premier League table after a 2-0 win over Leicester at Old Trafford on Saturday. It is the second season in a row that Mourinho's team have had a 100 percent record after three games.

Mourinho has enjoyed the luxury of having a week of preparation time for games against West Ham, Swansea and Leicester but that will end when his players return from their international commitments.

United played just four competitive fixtures in August but face seven in September, including a League Cup tie with Burton and Champions League games against Basel and CSKA Moscow.

Mourinho said: "I have to say something that I felt once in my career that I was not playing in European competitions, if I had one week to prepare a match my team is always very good because we have time to organise a week of work going through every item of the game, when you start playing every two days it's more based on what you build during preseason that is not going to be repeated.

"From now, no more clean weeks until the moment we are out of one of the cups, so now my team is the mirror of the work we are doing in clean weeks where we can train five days and go through every item of the gameplan."

Mourinho has also revealed he has concerns over Jones' fitness.

The 25-year-old has been a key part of a United defence that has gone more than seven hours without conceding a league goal, a run stretching back to May 14.

But he could now face a spell on the sidelines after the United manager revealed he has picked up an ankle problem.

However, the injury did not stop Jones from meeting up with the England squad as planned on Sunday ahead of World Cup qualifiers against Malta and Slovakia.

Mourinho said: "He's potentially a very good player, he's still young and in a learning age but for years and years and years he was injury prone and he has a problem now, he has a problem now, he's complaining about an ankle problem so he's the kind of player where we need to have him always in our hands with a lot of care from the medical department the fitness coach, my assistants in the gym, working on prevention and recovery.

"If we manage to have him safe from injuries he is everything I like in a central defender."

Even if Jones shakes off the injury, he will still miss the first Champions League group stage game against Basel at Old Trafford on Sept. 12 while he serves the second game of his UEFA suspension, a punishment United have appealed.

Eric Bailly is also suspended, meaning new £31 million defender Victor Lindelof, who was not even in the squad to face Leicester, is set to start.

Mourinho added: "Eric is playing really well, Smalling is in very good conditions and Victor is improving every day so, as you know, against Basel Jones and Eric are suspended so against Basel we will play Victor and Smalling."