Sanchez suffered a bang to his knee during the first half at the Emirates Stadium and Arsene Wenger was ready to substitute him at half-time but the Chilean insisted he could continue. The 26-year-old was returning from a two-week lay-off with a hamstring problem but his latest setback is more of an impact injury and considered to be only a minor knock. Sanchez could even play in this weekend’s FA Cup fixture, although Wenger may choose to rest his leading scorer with a busy schedule to come. Ramsey’s diagnosis is more severe. The midfielder is undergoing tests from Arsenal’s medical team but will not return before the Champions League last-16 first leg tie against Monaco on February 25. The club are reluctant to place a timescale on Ramsey’s recovery, particularly given the concerning regularity of the Welshman’s fitness problems this season. He missed three weeks after injuring his hamstring against Tottenham in September and was out for almost six weeks following a recurrence in December. “Yes, it is his third hamstring injury this season,” Wenger said after the game against Leicester. The news on Aaron Ramsey’s latest hamstring strain is, however, less positive with the Gunners midfielder certain to be out for a fortnight at the very least. Sanchez and Ramsey both had to be taken off in the second half of Arsenal’s 2-1 win against Leicester on Tuesday. “Last year it was a thigh injury but this year it’s a recurrence of hamstrings. “You cannot say it’s not a worry because after a while the player doesn’t play with the freedom in the mind. “He’s not overplayed. Before I just played him in every game but since he’s had these problems, I’m a bit more cautious with him.” Press Association Alexis Sanchez’s knee injury is not considered serious and the Arsenal striker is expected to be available for Sunday’s FA Cup tie against Middlesbrough.