Real Madrid star Cristiano Ronaldo remains doubtful for the first leg of their Champions League semi-final tie with Bayern Munich on Wednesday.

Ronaldo, who has scored 14 goals in eight Champions League appearances this season, has missed Real Madrid's last four games, including the club's 2-1 win over Barcelona in the Copa Del Rey final last week.

Real Madrid coach Carlo Ancelotti told ESPN FC that Ronaldo, who is still nursing a thigh and knee injury, has trained with the club over the past two days, but it still unknown whether or not he will be fit enough to play on Wednesday.

"Cristiano trained normally today, he has trained well these last days," Ancelotti said. "Tomorrow we will have another test to be sure. He wants to play and we are confident, but the decision will be made tomorrow. If there is a risk he will not play."

Ancelotti stressed that he is taking a cautious approach on Ronaldo's return, fearing that the Portugal international might aggravate his injury that could force him to miss the second leg next week.

The 54-year-old Italian manager revealed that the best possible scenario on Wednesday is for Ronaldo to come in as a substitute even if he is fit enough to start for the club.

"He feels good, we feel good, tomorrow we will do a physical test and if he feels good he will play," Ancelotti said. "The tie will not be decided [in the first leg], maybe we will get an advantage, but it will be decided next Tuesday. We must also think whether Cristiano on the bench could give us more options. Any minute could be the decisive minute."

Gareth Bale, who score the game-winner in last week Copa Del Rey final, missed the team's training on Monday due to flu, but Ancelotti revealed that the 24-year-old midfielder will play on Wednesday.

The second leg of the Real Madrid vs Bayern Munich Champions League semis match is scheduled on Tuesday, April 29, at the Allianz Arena in Germany.