Arsenal midfielder Mikel Merino is expected to be out for an 'extended period' with a foot injury and may not feature again this season. He is set to undergo surgery on the issue, which he sustained late in the defeat against Manchester United last weekend. Arsenal are thought to be considering emergency measures in the winter transfer market to cover for the absence of the 29-year-old.Merino was absent from Arsenal’s 4-0 win at Leeds United on Saturday and Arteta confirmed that this was due to a foot injury. A subsequent statement by the club on Sunday confirmed that Merino has a bone injury and will be required to undergo surgery in the coming days. The statement continued that Merino will be out for an "extended period", with the club aiming to have him back in training before the end of the season.David Ornstein of The Athletic claims that the Gunners are considering bringing in a short-term emergency option to replace Merino on deadline day, possibly on a loan move, though there are "no guarantees" of anything materializing at this late stage in the window.Merino has made 33 appearances for the Gunners this season and has provided a useful utility option for Arteta in multiple roles, including in midfield and as a makeshift striker – where he also often features for his native Spain. Merino is set to miss the March internationals but will hope to be fit to represent his country at the World Cup in the summer.Speaking in a press conference earlier in the season on Merino's ability to fill in at striker, Arteta said: “Yes, as a striker certainly not [something he ever dreamt he could do] but that’s the thing as well that you learn when you sign a player – I knew he could offer much more than what he had, and especially after I met him for the first time because a player that has that amount of curiosity, the way he loves his profession and football, it’s difficult to put limits to that.”Premier League leaders Arsenal have endured several injury issues this season to the likes of Bukayo Saka - who also missed the win at Leeds - in addition to previous time out for other such as Martin Odegaard, Gabriel and Riccardo Calafiori, while strikers Gabriel Jesus and Kai Havertz have only just returned from long-term lay-offs.The Gunners are hoping to end their 22-year wait to win the league title and also topped the Champions League opening phase with a perfect record, while Arteta’s side also remain in both domestic cups. Add GOAL.com as a preferred source on Google to see more of our reportingMerino will definitely be absent when Arsenal host Chelsea in the second leg of their Carabao Cup semi-final tie on Tuesday, which they head into with a 3-2 aggregate advantage. Arteta's side are set to face Sunderland at the Emirates in the Premier League four days later as they continue their push for domestic glory.