Arsenal manager Arsene Wenger admits he has regrets over a series of transfer decisions he made which contributed to the club's failure to challenge for silverware this term. The Gunners are fighting for second place on the final day of the Premier League season, rather than for the title, while their domestic cup and European campaigns ended prematurely.

Wenger decided against signing a single outfield player during the summer transfer window – with Petr Cech's arrival from Chelsea representing the only significant addition – before Mohamed Elneny joined from FC Basel in January. Long-term injuries to Jack Wilshere, Danny Welbeck and Santi Cazorla then exposed the decision as the club's trophy ambitions fell away.

"You don't think I am in the game 35 years and I don't look at myself? I am not pretentious enough to do that," the Arsenal boss told reporters when asked how he will reflect on the 2015-16 campaign. "Of course I look at myself and what I could have done.

"I must say it was very difficult for us because Welbeck came back in April and it was very difficult to envisage that he would be out for such a long time. Cazorla was out for five months. Could we have done something? We brought in Elneny who has done extreme well but we got [Alex] Iwobi out of the youth academy who has done extremely well.

"You must say that you do not find in January players extremely available. Of course I think about myself and what I could have done and what kind of decisions that I did not get right."

The club's plans for next season have already been rocked by the news Welbeck will miss the next nine months with a second knee injury in as many seasons. The former Manchester United striker returned from a knee issue in April but following nine starts is back out on the sidelines. Wenger admits the blow could force Arsenal to alter their plans for the summer transfer window.

"It's a good question," Wenger admitted. "We have to think about that. When a player is out for nine months you have to consider that it is for the season. it makes you short on the striker front. I don't think so [it will be harder to sign players without signing a new contract]. I hope not."

Welbeck's latest injury has potentially opened the door for Theo Walcott to be included in England's European Championship squad. The tournament would put the 27-year-old, who has started one of Arsenal's last 13 games, in the shop window amid reports West Ham United are interested in the ex-Southampton forward – rumours Wenger has rebuffed. "Yes [my instinct tells me he will be at Arsenal next season]," the Frenchman said. "He will be here yes."

Three players who are destined to leave Arsenal are out-of-contract trio Mathieu Flamini, Mikel Arteta and Tomas Rosicky. Wenger has indicated the visit of Aston Villa represents their final game for the north London club.

"I believe that Mikel Arteta is the captain of the club and he has been a great leader and all these players we have to decide do they go on with their careers as a player or a coach," he stated. "Tomas Rosicky has been with us from 10 years. I think everybody loves him as well. Flamini has been an extremely strong leader on the pitch and off the pitch, so we lose three big personalities. No-one definitely leaves Arsenal."