The coach insisted his star forward was just brought off as a precaution and praised his team following their confident 3-0 win over Dortmund
Wednesday's quarter-final first leg marked another high point in the Ballon d'Or-winner's incredible campaign, as he equalled Lionel Messi's record of 14 Champions League goals in a season during the 3-0 win over last season's European runners-up.
The Portugal captain was booed by his own supporters during Saturday's 5-0 thrashing of Rayo Vallecano at the Santiago Bernabeu, but his name was being chanted after he scored his side's third goal against Dortmund to take his tally for the season to 45.
Ancelotti revealed last week that Ronaldo was carrying a minor knee injury and the Italian brought the former Manchester United man off with 10 minutes remaining against the side who beat the Spanish giants in the semi-final last term.
But the Italian coach played down concerns that his prolific forward could face a spell on the sidelines at such a crucial stage of the season, as his side attempt to win a Champions League, La Liga and Copa del Rey treble.
"Cristiano had a knee injury," Ancelotti told reporters. "I've taken him out to avoid risks. He is not injured, just a minor annoyance."I'm satisfied with the result and the attitude of the team. It wasn't an easy game but we started well. Then we slowed down and Dortmund are a very dangerous team on the break.
"Now we have to play in Dortmund. They use dangerous and quick counterattacks, but our defence was good. We also pushed up to stop them doing long balls."