Champions League: Cristiano Ronaldo remains doubtful for 2nd leg against Manchester City

Madrid: Real Madrid has been keeping quiet about Cristiano Ronaldo's injury, and his presence in the second leg of the Champions League semifinals is likely to remain a mystery until just before next week's game against Manchester City.

Ronaldo underwent new tests on his injured hamstring on Wednesday, but Madrid did not reveal the extent of the problem or how long the Portugal forward will remain sidelined.

He was expected to play in Tuesday's first leg in Manchester, but watched the 0-0 draw from the bench after failing a physical just before the game.

There have been widespread rumors about the injury, but the only clue since the game has come from a post on Ronaldo's official Instagram account, which simply said, "Don't worry be happy," along with a photo of him smiling. He later also posted photos of him exercising in a gym, including one where he is flexing his muscles.

Before the game in England, television cameras caught him saying that he still wasn't fully fit.

"I'll wait for the next match," he said in Portuguese, apparently while talking to other players. "If it was a final, I would play."

Spanish media has published various versions of the injury, from a full muscle rupture that will keep him out for the rest of the season to a minor ailment that should heal quickly.

The sports daily AS suggested that Ronaldo would undergo "stem cell treatment" to try to recover in time for next week's game at the Santiago Bernabeu in Madrid.

Coach Zinedine Zidane spoke only briefly about Ronaldo following Tuesday's game.

"He felt something and wasn't comfortable," Zidane said. "Hopefully he will be fit for the second leg."

The coach and other team officials had previously downplayed the problem, saying the forward would likely be ready for the first leg.

Ronaldo picked up the injury toward the end of a 3-0 win over Villarreal in the Spanish league on April 20, when he tried a volley inside the area and fell awkwardly. He seemed to be in pain and, after getting up, put his hand on the back of his right leg. Ronaldo walked off the pitch just before the final whistle, leaving the team with 10 men.

It's almost certain he will miss Saturday's Spanish league game at Real Sociedad, having been sidelined for last Saturday's 3-2 win at Rayo Vallecano. His team is one point behind Barcelona and Atletico Madrid with three rounds to play.

Ronaldo had played in every Spanish league game this season, and had scored seven goals in his previous seven matches in all competitions before missing the game against Rayo.

He is the leading scorer in both the Spanish league and the Champions League, where he has 16 goals from 10 games, one shy of the record he set in the 2013-14 season, when Madrid won its 10th European title.

Zidane may also be without forward Karim Benzema, who left Tuesday's game because of a knee problem that has been bothering him for some time.

"They are two important players and we hope that they are back for the second leg," Zidane said. "We'll take it day-by-day and look at it with the doctors."