MADRID, Sept. 18 (Xinhua) -- Real Madrid kick off the defense of their Champions League crown with a home game against AS Roma on Wednesday night with question marks still hanging over the performances of coach Julen Lopetegui's side.

Saturday's 1-1 draw away to Athletic Club Bilbao has again provoked doubts over the club's ability to compete for the Spanish League and Champions League titles without Cristiano Ronaldo.

Although Madrid began their season with three wins in La Liga, in their game against Girona, two goals came from the penalty spot, while against Leganes the score was inflated by late goals scored on the break.

However, against an Athletic Club Bilbao team that didn't make many mistakes, Gareth Bale, Karim Benzema and Marco Asensio failed to break down a well-organized defense.

The introduction of Casemiro as a second half substitute gave Madrid more control at the weekend and he is certain to return at the expense of Dani Ceballos on Wednesday.

New signing Mariano was on the bench in Bilbao and the fact that he wasn't introduced as a second half substitute when Madrid were searching for a winning goal was also commented on in the press. Mariano will hope to make his first appearance in his second spell at the club at some point during Wednesday's match.

Meanwhile it will be interesting to see if Lopetegui decides to continue with Thibaut Courtois in goal or to use Europe as the chance to give minutes to Keylor Navas, who has lost his place to the Belgian international.

Should Lopetegui opt to play Navas in Europe that could solve a problem, because if Navas is to be a substitute in both major tournaments, he could look to move in January.

Roma have had a slow start to the season in Serie A with just one win from their first four games, with that victory coming away to Torino on the opening day of the campaign. This weekend saw them held to a disappointing 2-2 draw at home to bottom of the table Chievo Verona.