Petr Cech is likely to miss two to three weeks after picking up a suspected hamstring injury in Arsenal's win over Watford, according to Unai Emery.
Veteran goalkeeper Cech hobbled off late in the first half at Emirates Stadium after hurting himself in the process of a goal-kick.
Bernd Leno stepped in for his Premier League debut and did not waste the opportunity, making fine saves from Troy Deeney and Roberto Pereyra in the late 2-0 victory.
The Germany international now appears set to stay in the side at least until the international break, potentially giving him matches against Qarabag and Fulham to make a claim for more regular minutes.
Asked by Sky Sports whether Cech's injury was serious, Emery replied: "I think no, but usually we will find out more tomorrow [Sunday]. I think two or three weeks."
Leno's twin saves came with the scores still level and set the platform for Arsenal's eventual victory, sealed courtesy of Craig Cathcart's own goal and a close-range Mesut Ozil finish.
Emery expressed confidence in the former Bayer Leverkusen gloveman with a first-team opportunity beckoning.
"I spoke with him and said the most important thing is, when the team needs him, to be prepared," the Gunners boss added in his post-match news conference.
"He did that on Wednesday and today. We have three very good goalkeepers. I think Bernd Leno can learn from Cech.
"I am very happy with him. He is working every day for his moment."
Watford head coach Javi Gracia was less appreciate of Leno's display as it cost the visitors what could have been three points, instead leaving them with a third defeat in four competitive outings.
"I'm a little bit disappointed because I think we have done a great performance and I think we deserve more than this result," Gracia told the BBC.
"We created clear chances and there were some amazing saves from the goalkeeper. We created more chances, had more shots on target, but we lost."
