Arsène Wenger has told Thomas Vermaelen that the Arsenal club captaincy will not guarantee him a first-team recall, as he considered whether to persist with Laurent Koscielny and Per Mertesacker in central defence at Swansea City on Saturday.

The manager said he was vexed as to why Vermaelen's partnerships with Koscielny and Mertesacker had spluttered at times, saying: "Sometimes there are mysteries in our game that are difficult to rationalise."

Wenger dropped Vermaelen for Wednesday's Champions League last-16 second leg at Bayern Munich and watched Koscielny and Mertesacker impress in the 2-0 win, which was the first time that the German team had been shut out all season, even if it was not enough to prevent Arsenal from exiting the competition on away goals.

He said that "the last game decides the next one" in terms of team selection, which suggested he was ready to stand by the defence which started against Bayern, although he will replace Kieran Gibbs with Nacho Monreal at left-back, Gibbs having suffered a recurrence of his thigh injury.

If Wenger sticks with his Bayern line-up, it would spell frustration for the goalkeeper, Wojciech Szczesny, who was rested in Munich and saw Lukasz Fabianski perform convincingly in place of him.

Wenger made it clear, though, that his decision over Vermaelen would not be influenced by the captain's armband, which he awarded to him last summer, and he gave the impression that he regarded it as a peculiarly English attitude that the captain ought to be the first name on the team-sheet.

"Who is a captain and a leader shouldn't guarantee you a place in any team," Wenger said. "In England it's true ... the captaincy is of massive importance.

"But for purely sporting reasons, or tactical reasons in the game, when you don't think it is the right selection, do you put the player in just as he is captain? That is disrespectful to the guy who doesn't play. For sporting reasons, it is not completely justifiable," he added.

Wenger feels Koscielny's partnership with Mertesacker has a nice balance to it, even though both are right-footed and ought to dovetail more easily with the left-footed Vermaelen.

"They do well together, it is true, [but] I can't see any obvious reason why Per and Vermaelen should not do well together," Wenger said. "I have played as well in some big games Vermaelen and Koscielny together and you think that should work as well because they are two good football players. One is right-footed, one is left-footed ... so they have all, at the start, to complement each other well. Sometimes there are mysteries in our game that are difficult to rationalise."

Wenger said Vermaelen had been hindered by a niggling ankle injury, even though he was tough enough to play through the pain – "Sometimes the performance suffers a little bit from that," Wenger said – while he also praised Koscielny, who has had his own fitness problems this season.

"He was outstanding against Bayern," Wenger said. "He has shown a bit more authority than usual and, when he does that, he gets his qualities completely out. He got a calf injury in our final pre-season game in Cologne and it took him a long, long time to come back and he has had many setbacks through the season. Every time he was close to coming back he had another injury or sickness. He has been sick a lot this year."