LONDON (AP)Arsenal left back Kieran Tierney is set to miss the rest of the season because of a knee injury that requires an operation.

Tierney felt discomfort after a training session on Thursday and was absent for Arsenal’s 3-0 loss at Crystal Palace in the Premier League on Monday.

The Scotland international underwent scans and following a consultation on Tuesday, it was decided he should have surgery on the problems ”in the forthcoming days,” Arsenal said.

”Kieran’s rehabilitation program will start immediately after his surgery, at which stage a clearer understanding will be established on his recovery timescale,” the club said. ”However, it is likely that Kieran will now miss the remainder of this season.”

Scotland will hope Tierney is fit enough to play in the team’s World Cup playoff match against Ukraine in June. The winner will meet Wales later that month for the right to play in the tournament in Qatar.

Tierney’s absence could prove to be a big blow to Arsenal’s chances of qualifying for the Champions League, with manager Mikel Arteta not having a senior backup at left back. Nuno Tavares, a 22-year-old Portuguese, has filled in for Tierney for two matches since the turn of the year and was brought off early on both occasions.

Arsenal is fifth in the Premier League, behind north London rival Tottenham on goal difference, in the race to finish in the top four.

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