Ronaldo is the competition’s leading marksman this season with 11 goals, a record for the group phase.

Zidane, a Champions League winner playing for Real in 2002, said Ronaldo was on top of his game after the Portuguese scored twice in Saturday's 4-2 Liga win over Athletic Bilbao.

“Cristiano is very important on the wing because when he attacks one-on-one he’s very good... he’s very hard to defend against,” Zidane added before the game at the Stadio Olimpico. “That’s how we scored the first goal (against Athletic).”

Left back Marcelo has recovered faster than expected from a shoulder injury that forced him to miss Saturday’s home game, was back in training on Monday and named in the match squad.

“We have to be especially wary of the speed of (Roma’s) players because that could hurt us,” Real striker Karim Benzema was quoted as saying in Mundo Deportivo.

“They’re going to play to win because it’s a very important game for them at home. We must win too because we know that to qualify the key is the first leg... If we’re at our best we’ll win.”

Isco looks certain to play in central midfield with Zidane saying he gave Mateo Kovacic a game against Athletic to rest the Spaniard, who has been a regular alongside Toni Kroos and Luka Modric under the Frenchman.

The match pits two recently appointed coaches against each other after Zidane and Luciano Spalletti took charge last month.

Spalletti returned for a second spell at Roma, who are on a run of four wins in Serie A, to replace Rudi Garcia.

Spalletti will have been pleased to see striker Edin Dzeko end his three-month scoring drought with a goal in Roma’s 3-1 win at Carpi on Friday, although the man Real must especially guard against is winger Mohamed Salah, who also netted.

Garcia’s tenure effectively ended with the 6-1 drubbing by Barcelona at the Nou Camp in the Champions League group stage, a result they will want to put firmly behind them on Wednesday.