According to Arsène Wenger, "we have all played with micro-fractures". Most of the time, the Arsenal manager said, "you don't even notice them." Arsenal, however, have noticed the micro-fracture to Kim Kallstrom's back and the club's lone January transfer market addition will not play for at least four weeks and more likely six. It could be even longer.

The situation is curious, to say the least and on one level, it highlights the craziness of the mid-season window, when so many compromises have to be made. On another level, it invites ridicule. Wenger has moved to address a midfield selection crisis, which has left him without Mathieu Flamini, Jack Wilshere and Aaron Ramsey for time scales that range from one or two to about six weeks with a midfielder who will be unavailable for about six weeks.

Wenger's justification was priceless. To paraphrase, and hopefully not too unfairly, he said that his midfielders were always picking up injuries and so when Kallstrom was ready, there would surely be further problems and the Swede could ride to the rescue. Wenger is not planning for this selection crisis but the next one.

Financially, as Wenger was keen to stress, there was no risk. Kallstrom's parent club, Spartak Moscow, have agreed to bear the cost of his wages until he is fit and there was no loan fee for a player who has not started a game since the league fixture against Zenit St Petersburg on 10 November.

Kallstrom has since been an unused substitute twice and an 84th-minute introduction against Rostov on 8 December – Spartak's last match before the Russian winter break, from which the league has yet to emerge. Kallstrom hurt his back during Spartak's warm-weather training camp in Abu Dhabi.

It is important to make the point that Arsenal's medical department detected the problem after a CT scan. Kallstrom's injury was not a post-transfer window shock which would have been embarrassing. The medical staff informed Wenger, they had warned him and it is not difficult to imagine them saying, "Arsène, are you sure that you want to do this?"

Wenger did wobble. Were he to have had two or three more days to sign somebody else, he would not have taken Kallstrom but it was 5pm on deadline day. What is a manager to do? It was better to take a decent player like Kallstrom for the run-in than to get no one at all. And Kallstrom is a decent player. Nobody wins 108 caps for Sweden by accident.

The story framed the visit of Crystal Palace to the Emirates Stadium but Wenger was simply happy to inhabit a world that was no longer shaped by Sky Sports' Countdown To Deadline Clock, and all of the shouting that goes with it.

Wenger has long since grown weary of the modern football theory that says the chances of trophies are in direct proportion to the number of pounds that are spent on players' fees. Throughout January, he had rolled his eyes, smirked and spoke in Wenger-speak when he was asked about new signings, even though there is always the desire among Arsenal supporters to see him spend some money.

It was very clear that Wenger wanted to say that Arsenal were at the top of the table, with the possibility of a serious title challenge, thanks to a group of players who had done pretty well over the first half of the season and it would be no hardship to soldier on with them. Chelsea and Everton added a couple of signings for the second half of the season but the other top six clubs did nothing.

Wenger often gives the impression that he is an accumulator of technically gifted, attack-minded midfielders – they are his version of a comfort blanket – and with the squeeze on because of Flamini's suspension and the injuries to Wilshere and Ramsey (the latter, a serious one), it was no great surprise to see him reach out for reinforcements. Wenger tried for Julian Draxler but the Schalke prospect was too expensive. He was also injured, although that is evidently no deal-breaker.

It was a midfielder that emerged from injury-induced misery who made the difference against Palace and how could it have been anything else? This was Alex Oxlade-Chamberlain's first Premier League start since 17 August and what Wenger called, with a touch of sarcasm, "the famous day against Aston Villa". Oxlade-Chamberlain was on the wing back then, when he suffered serious knee ligament damage but Wenger sees the England international's future in central midfield and the 20-year-old offered an illustration as to why.

With Mikel Arteta doing what Mikel Arteta does, namely provide security and not waste the ball, Oxlade-Chamberlain drove forward and he tried to make things happen. There were one or two mistakes from him in the first half but he continued to show for the ball and, in the second half, the shackles came off.

The catalyst was his first goal since December 2012, a beautiful finish from a pass by Santi Cazorlaand, thereafter, he enjoyed himself. There was urgency to his passing; power and acceleration to get away from pressure. The second goal showcased everything that is good about his game. Wenger has his new central midfielder, after all.