Arsène Wenger has rejected the allegation that Arsenal have gone backwards in the Premier League this season, arguing that the club’s horrendous injury problems have simply been too much.

Arsenal were level on 36 points with the leaders Liverpool on Christmas Day last season whereas this time out – also after 17 matches – they have 27 points and sit in sixth place. They trail the leaders, Chelsea, by 15 points.

Wenger is happy with the impression that his summer signings have made, with Alexis Sánchez having been particularly impressive. Danny Welbeck and Calum Chambers have contributed while Mathieu Debuchy has shown his quality in flashes, before and after his long-term ankle injury. David Ospina, the back-up goalkeeper, has been held back by thigh trouble.

Wenger’s frustration has been located in the sheer number of serious fitness problems that key players have suffered and there have been numerous shorter-term issues, too. The manager maintains that the after-effects of the World Cup have been a factor, with the France trio of Debuchy, Laurent Koscielny and Olivier Giroud each succumbing to lengthy lay-offs, together with the German World Cup winner Mesut Özil.

“I don’t think we have gone backwards in the quality of our squad,” Wenger said. “If you look at the five players that we bought [Alexis Sánchez, Danny Welbeck, Calum Chambers, Mathieu Debuchy and David Ospina], you cannot say that one of them is a failure. I can’t deny that we are behind much more than last year because we had a depleted squad since the start of the season and no stability. The fact we got so many important injuries at the back cost us too much. We lost Debuchy and Koscielny at the same period for three months. It’s too much.

“We had too many players who came back after the World Cup not ready to compete again and then you look at the number of players that we lost when they just came back to their best. We had no Walcott, no Wilshere, no Özil, no Debuchy, no Koscielny, no Giroud, no Arteta for long periods. It’s like you have half of the squad out.”

Wenger is engrossed in the chaotic enjoyment of English football’s festive programme – his team begin with the visit of Queens Park Rangers to the Emirates Stadium on Boxing Day. He noted how plenty could change over the period, although he said that Arsenal and the clubs around them would “need to be massively consistent to have a chance to come back” into the title race.

He believes, though, that the Premier League ought to schedule an annual break in January. “I think it would be good for the English national team,” he said. “Respect the English tradition [of festive football] and then give a winter break in January.

“If you look at the history, is it a coincidence that the German national team has always done well in the big tournaments when England hasn’t done so well? Germany has the longest winter break in Europe, among the big countries, and, by coincidence, they always do well in tournaments because they have refreshed players.”