Arsenal midfielder Aaron Ramsey has picked up another hamstring injury.
The 24-year-old pulled up in the 56th minute of the Gunners' Champions League 2-0 victory at home to Bayern Munich on Tuesday and was replaced by Alex Oxlade-Chamberlain.
Manager Arsene Wenger confirmed: "He is alright but very down because he told me that his hamstring is quite a tough one. He is out."
Ramsey suffered hamstring problems on three separate occasions last season, the most recent of which kept him out for three weeks in February.
The Wales international also spent periods out in September and December of last season with the same injury.
He missed three weeks after injuring his hamstring on September 27 against Tottenham and then spent over six weeks out over the busy Christmas period after re-injuring the muscle in the Champions League win at Galatasaray on December 9.
Ramsey has started all nine of Arsenal's Premier League games so far this season and the club are set to assess him ahead of their next match against Everton on Saturday.