The injury that forced Karim Benzema off the field in Real Madrid's victory over Celtic "does not seem like anything serious", according to Real Madrid head coach Carlo Ancelotti.

Benzema hobbled off with half an hour played of Tuesday's Champions League win in Glasgow after pulling up with a knee issue.

The France international had made a fast start to the campaign with five goal involvements in his first five outings prior to sustaining the injury at Celtic Park.

Any sort of lay-off for Benzema would be considered a major blow for Madrid during a busy period, but Ancelotti provided a positive update after the match.

"It doesn't seem like anything serious. Tomorrow they will do more tests," he told Movistar. "It could be that he is just suffering some discomfort."

Madrid battled to a 3-0 victory in Benzema's absence, with replacement Eden Hazard rounding off the scoring after Vinicius Junior and Luka Modric had put the visitors in control.

The reigning European champions survived a number of scares prior to Vinicius' 56th-minute opener, but their quality and experience told in a ruthless second-half showing.

"We played against a team that put in a lot of intensity and we had to suffer a bit," Ancelotti said. "We weren't effective in the last third and lacked speed.

"But that changed in the second half. We know the first half could have been better, but the second was pretty much perfect."

Hazard's goal was just his second for Madrid in the Champions League, coming at the end of a brilliant 33-pass move that carved Celtic open.

No player created more chances than Hazard (three), despite the Belgium international playing only an hour, and Ancelotti was impressed with his performance.

"I thought it was the right game for Eden," Ancelotti said of his decision to bring on Hazard for the injured Benzema. 

"The two central defenders didn't jump much under pressure, and his position not as a striker but a little more from behind could help us. 

"We didn't ask Eden to put in the work of [Federico] Valverde or others, but to instead do other things.

"He's motivated in training, and although it was difficult for him to get into the first half, he was decisive in the second. It's important for us and hopefully he can continue."

Madrid have now won all four of their away group matches in the Champions League since the start of last season without conceding, netting 12 goals of their own.

They have won all six matches played in all competitions this season, meanwhile, but goalkeeper Thibaut Courtois accepts his side did not have it all their own way against Celtic.

"The first half was difficult," he said. "Celtic started strong and there was a great atmosphere here after so many seasons out of the Champions League.

"They made it hard for us to get going. We didn't start well and they hit the post. But eventually we found our rhythm and dominated the second half for a deserved victory."