Arsène Wenger has challenged his players to prove they deserve to be at Arsenal next season, saying their performances will determine the decisions he makes in the summer and hinting that he is ready to be ruthless with those who fail to meet his expectations.

Arsenal, who host Reading on Saturday afternoon, are four points behind fourth-placed Tottenham and are in danger of failing to qualify for the Champions League for the first time in 16 years. While they have a game in hand on Spurs, Wenger's position at the club has never been under so much scrutiny and whether the players who are currently at his disposal are good enough to relieve the pressure on him remains to be seen.

"We have five players for the England team and 22 international players," Wenger said. "So we have to analyse. What will decide our attitude, my attitude, is how we do now until the end of the season. What is important is we look at how we finish the season, how well we play – and make the decisions on who to buy and who to sell at the end of the season. This will be influenced by the way we play in our last nine games." The message to Arsenal's players is that their future is in their own hands and overhauling Tottenham, as they did last season, will vindicate Wenger's faith in them. Losing to Blackburn Rovers in the FA Cup and Bradford City in the Capital One Cup had threatened to derail Arsenal's season, and they could have collapsed after the 2-1 defeat by Tottenham on 3 March left them seven points behind their rivals.

However, the gap has been reduced since then and Wenger has been pleased with his side's response in impressive victories away to Bayern Munich and Swansea City, even though winning 2-0 in Germany was not enough to prevent Arsenal from exiting the Champions League on away goals.

Injuries will test them against Reading and Wenger has expressed concerns over his lack of options in midfield. Jack Wilshere, who has not played since the defeat by Tottenham, is missing for another two weeks with an ankle injury, while Abou Diaby has been ruled out for nine months after tearing the anterior cruciate ligament in his left knee in training on Wednesday. Theo Walcott is also out for 10 days with a groin injury, while Kieran Gibbs is struggling with flu.

"They have gone through difficult times and have responded well," Wenger said. "They have shown mental strength as we lost against Blackburn, Bayern and Tottenham. So, as well, they could be scared that the group implodes. We have shown a strong response against Bayern and Swansea, and that shows that the group is mentally strong.

"What is for sure is that we had some blips in this season, but we did not expect the defeats to Bradford and Blackburn. But, overall, the attitude of the team has been great and when everybody is here we have a strong team. What is important is to analyse where we can improve at the end of the season."

The sale of Robin van Persie to Manchester United last summer has been pinpointed as the source of Arsenal's problems, but Wenger insisted he is not short of attacking talent. "Podolski, Giroud, Walcott and Cazorla can all score goals," he said.

"We have shared more than last year. We didn't score less goals. Where we haven't done it this season is in the big games. This year we are bottom of the league with the big teams. It's difficult to know why. Not because we have been dominated. We were never inferior possession-wise, but just because, after 20 minutes, we were chasing in every game."