Alexis Sánchez
Alexis Sánchez is the latest Arsenal player to be set for a spell on the sidelines with injury. Reuters

It is a case of one step forward, two steps back for Arsenal on the injury front. While Theo Walcott could be available to make his return against Sunderland on Saturday, Alexis Sánchez and Santi Cazorla will be out, although with a more precise prognosis remaining unclear.

Walcott has been out since the end of October, after picking up a groin injury just minutes after coming on in a Capital One Cup match against Sheffield Wednesday. But, along with Laurent Koscielny, who had to go off with a hip injury in Sunday’s 1-1 draw with Norwich City, and Kieran Gibbs, who sat out that most recent encounter, he has a chance of being involved at home to Sunderland.

“We will make a decision on Saturday on Koscielny and Walcott, they could both make the squad,” manager Arsene Wenger told Arsenal’s official website on Thursday. “Gibbs is available again for the weekend.”

Still, Arsenal’s injury crisis is still a long way from being over. Already missing Francis Coquelin, Jack Wilshere, Danny Welbeck, Tomas Rosicky and Mikel Arteta, the match with Norwich saw, not only Koscielny go down hurt, but two more influential players suffer more serious problems.

While Cazorla, who has started every one of Arsenal’s Premier League and Champions League games this season, finished Sunday’s encounter, he did so, according to Wenger, “on one leg.” It has been widely reported that the Spain international has suffered knee ligament damage and is set to miss at least three months. If so, it will mean Arsenal being without their first-choice midfield partnership of Cazorla and Coquelin well into the new year and for a crucial stage of the season.

Sánchez has been arguably the most influential player at Arsenal since he signed from Barcelona in the summer of 2014. His importance to the team has meant him playing almost every game, despite also doing so for Chile, both in World Cup qualifying and their run to the Copa America title in the summer. Yet, despite Wenger revealing that Sánchez had experienced a hamstring scare last week, he was still played against Norwich and duly suffered a hamstring injury. The 26-year-old is expected to miss at least three weeks, although, as with Cazorla, Wenger didn’t divulge any more details on Thursday.

“At the moment on Alexis, Santi and Mikel [Arteta], we don't know how long they will be out for,” he said.

There has been some official comment on Sánchez’s injury, however. Chile manager Jorge Sampaoli has revealed that Sánchez has been allowed to conduct at least part of his recovery back in his home country.

“We have contacted the medical team at Arsenal, who have given him a week of treatment in Chile,” he is reported to have told Chilean radio station Tele13. “We have to see how the injury is in order to know how quickly he can recover, but we are aware of everything and we'll see if we can contribute to Alexis getting back on the pitch sooner.”

If the initial prognoses prove accurate then both Cazorla and Sánchez will miss Arsenal’s decisive Champions League encounter at Olympiakos next Wednesday. Arsenal need to better Olympiakos’ 3-2 win at the Emirates Stadium earlier this season in order to progress to the last 16.