Manchester United manager Jose Mourinho says Marouane Fellaini was "lucky" to avoid serious injury following a challenge from Shane Long against Southampton.

Fellaini has been ruled out of the Champions League clash with CSKA Moscow on Wednesday after suffering an ankle injury following Long's challenge in the first half of United's 1-0 win at St Mary's on Saturday. Mourinho is also without Paul Pogba and Michael Carrick to further reduce his options in midfield.

But the United boss says Fellaini's injury could have been much worse -- although he does not blame referee Craig Pawson for only showing Long a yellow card.

"For me Craig Pawson is one of the big talents in refereeing in England," Mourinho told a news conference in Moscow on Tuesday. "He had an amazing game in my opinion. He was so calm and in control and I think he had a great performance.

"After I watch it on television, no camera for Craig, and he made that decision. Fellaini was lucky, it could be a much worse situation but in a moment when we don't have Pogba and Carrick, Marouane becomes even more important than he always is. For him not to be here is a difficult situation for us.

"We don't have Fellaini, we don't have Pogba, we don't have Carrick. So all three midfield players we lose for this match. The solutions are not many but we try not to focus on individual battles or specific areas of the pitch. We are going to have a team with quality, with balance and to try to win the match which is our objective."

Fellaini is also set to miss Crystal Palace's visit to Old Trafford in the Premier League on Saturday before the two-week international break, with a trip to Anfield to face Liverpool following on Oct. 14.

Marouane Fellaini is sidelined with an ankle injury. Michael Regan/Getty Images

Belgium have already qualified for the World Cup in Russia next summer, and Mourinho has suggested coach Roberto Martinez should consider omitting Fellaini from the squad to play Bosnia on Oct. 7 and Cyprus on Oct. 10.

He added: "I don't expect Fellaini to be out for a long time and after Crystal Palace there is the international break, and Belgium, I think, was the first team to qualify, so not under pressure for a special big match. Hopefully he will be back for us."

Mourinho will be without Fellaini against Palace, but he will be allowed on the touchline after the Football Associated decided not to take further action against him following his sending off against Southampton for encroaching on the pitch.

Mourinho said: "If I am not punished it is because there were no reasons for the sending off so I am happy that was recognised and I can be doing my work normally against Crystal Palace. That is enough for me."

Like United, CSKA got their Champions League campaign off to a winning start with an impressive victory over Benfica.

Mourinho has faced CSKA during spells in charge of Chelsea, Inter Milan and Real Madrid and says United will not have it all their own way at the VEB Arena.

He said: "I always like to be back here because it is a beautiful city -- every time I come it's better and better -- so I have to say that it's a pleasure. Opponents-wise, I think it's the best CSKA side that I will have faced."