Laurent Koscielny Arsenal Demba Ba Besiktas
Arsenal are facing a defensive crisis following an injury to Laurent KoscielnyReuters

Theo Walcott might have returned to training, but the forward, so essential for a winning Arsenal team, will not feature in the English Premier League game against Hull City on Saturday, while Arsene Wenger has been dealt another major blow in the defensive department.

Walcott returned to training this week, a comeback which would have been met with much glee by Wenger and the fans. Without Walcott in the lineup in the second half of last season, Arsenal struggled to find their rhythm and form from the first half of the season, eventually tailing off and finishing in fourth spot.

The England international is set to play in the U-21s match against Blackburn Rovers on Friday, which rules him out from taking part in any shape or form for the match against the team that Arsenal beat to clinch the FA Cup last season.

"No [he won't play against Hull]. He will play on Friday night in the under-21s," said Wenger. "He has been out for nine months and needs to find some rhythm in the game and some confidence to go into the contact."

Another player who made a welcome return from a long-term injury – Serge Gnabry – is also unlikely to feature for the Gunners against Hull at the Emirates.

"Gnabry is like Walcott, he has been a bit more in and out, he had no big surgery," revealed Wenger. "But he is not completely ready today, he is even a bit behind Walcott. I don't think either of them will be involved."

Arsenal skipper Mikel Arteta, though, returns to the side, while their talisman Aaron Ramsey is set to resume training on Monday, following a hamstring injury, and should be available for the midweek Champions League game against Anderlecht. Yaya Sanogo will return to training next week, while Tomas Rosicky should be fit enough to play on Saturday after picking up a knock on international duty.

"Arteta is back in the group, and will be in the squad," said Wenger. "Saturday's game is too soon for Aaron. He will be back in full training on Monday and certainly in the squad for Wednesday."

That is pretty much where the reasonably good injury news ends for Arsenal, though, as Wenger revealed that Laurent Koscielny will miss the match against Hull City, and possibly even more, with a persistent Achilles problem, which forced him to return from France duty early.

"He has an Achilles problem, which has got worse," admitted Wenger. "He finds it difficult to play with it at the moment. You can only trust what the players says, he does not feel ready to play and will not play on Saturday. No [he will not need surgery]."

With Koscielny missing and Calum Chambers suspended, Wenger will be forced to play left-back Nacho Monreal, who himself is only just making a return from injury, at centre-back, while Hector Bellerin will have to fill-in at right-back.

Such a makeshift defence is exactly what could have been avoided had Wenger been more proactive and signed a central defender during the summer transfer window. However, as of now, Arsenal have to struggle their way through until at least January when the transfer window reopens again.

Also missing the game on Saturday will be David Ospina, along with long-term casualties Olivier Giroud, Mathieu Debuchy and Mesut Ozil.

Elaborating on Ozil's unexpected injury, Wenger said: "He told me [about the injury] once it was discovered on the scan. He did not tell me anything during the Chelsea game, I did not know.

"What happened was that at halftime, just before we went out, he had a little pain with his knee but it was not bad. He wanted to go on and I told him, 'If you don't feel well, tell me and I will take you off straight away'.

"He never did that during the whole game, and after I left him on because we were in a position where we needed to score a goal and he can deliver the final ball. Then after the game, he went to Germany. With Germany, they thought at the start it was nothing.

"We played on Sunday, on Monday he was off, and on Tuesday they gave him the day off. He was supposed to practice on Wednesday. On Wednesday morning, he said he could still not practice. They sent him for a scan, and in this scan they discovered that he a knee ligament injury which is quite serious."