Arsenal and Wales midfielder Aaron Ramsey is expected to be out for four weeks with a thigh injury.
That period would rule him out of games in the Champions League, Premier League and FA Cup, while he would also miss Wales' friendly matches against Northern Ireland and Ukraine.
The 25-year-old was injured in Tuesday's 4-0 FA Cup win at Hull.
"His signs are quite positive," said manager Arsene Wenger. "At the start I would say four weeks."
Among the games Ramsey will miss are Sunday's FA Cup quarter-final against Watford, Wednesday's Champions League last-16 second leg in Barcelona and a Premier League trip to Everton the following Saturday.
He is also set to miss Wales' Euro 2016 warm-up matches against Northern Ireland on 24 March and the away game in Ukraine on 28 March.