Arsenal captain Laurent Koscielny could return to first-team action sooner than first expected after head coach Unai Emery commented on his "very good progress" in training.
The France international has not played competitive football since he ruptured his Achilles tendon in the 12th minute of Arsenal's 1-0 defeat at Atletico Madrid in May, but Emery confirmed he is back in action at the club's training centre.
The Gunners have made a poor start to the season in Koscielny's absence, conceding five goals in their first two Premier League matches of the season, both of which ended in defeat.
Emery paired Sokratis Papastathopoulos with Shkodran Mustafi in the centre of defence as Arsenal were beaten 2-0 by Manchester City and 3-2 by Chelsea, but the Spaniard did not rule out a return for Koscielny when his side entertain West Ham on Saturday.
When asked about Koscielny's progress, Emery told reporters: "He's working very hard. He came back to us last Sunday.
"We are happy to have him here with us, because he's our captain and he's showing us his spirit to stay with us. We need to be patient with him because the injury was an important injury."
Pressed on Koscielny's likely availability, Emery replied: "It's difficult to know. You look at this morning, he's running, he's working on the pitch.
"The progress is very good progress."
With a win against Manuel Pellegrini's Hammers imperative for Arsenal after successive defeats, Emery was asked whether he is tempted to alter his formation to incorporate an extra striker.
Pierre-Emerick Aubameyang has played as a lone frontman in both of Arsenal's opening league games but Emery said he and his players are not averse to a change in formation if required.
"At the moment, I think we need to have the control with the possession, with the positioning on the pitch, with more players inside," added Emery.
"But it is one possibility to continue our progress and in one moment to try also to play with two scorers. In the last match of the pre-season, against Lazio, I did it with [Alexandre] Lacazette and [Eddie] Nketiah.
"But also, this position also for the players, they know that in one moment we can do that. But at the moment, no."