"I got a text last night (to say) that he has a hamstring injury," Wenger told beIN Sports. "The team from Chile has travelled without him and they kept him to try and get him fit to play Uruguay for the second game on Tuesday night.
"With a hamstring injury, we have to get access for our medical staff to the MRI scan to see what grade it is, how bad it is and make absolutely sure they don't make any suicidal decision that could harm his future for two or three months."
Arsenal have benefited from Sanchez's shift to the central striker's role as the agile forward has scored eight goals to propel the side to the top of their Champions League group and to fourth in the league, two points behind leaders Liverpool.
The French coach also said Chile should put Sanchez's health first despite the 27-year-old's overwhelming desire to represent his country.
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"It's a grey area between the national team and the club team and of course they look at their own results, which I can understand, but we have to preserve the health of Alexis Sanchez," Wenger added.
"He always wants to play and that's where it is a more sensitive case because he's always ready to play even when injured."
Arsenal's next fixture is a league match at sixth-placed Manchester United on Nov. 19.
(Reporting by Shravanth Vijayakumar in Bengaluru; Editing by John O'Brien)
