The defender, who made just his third league appearance of the season, was frustrated by the loss but expects Arsenal to return to winning ways after the international break
Thomas Vermaelen has rued Arsenal's "missed opportunity" in Sunday's 1-0 defeat to Manchester United, but has backed the Gunners to recover quickly.
The north London club had been unbeaten since losing to Aston Villa on the opening day of the season, moving to the summit of the Premier League, but fell to a first-half Robin van Persie header at Old Trafford.
Vermaelen admits the squad were disappointed with both their performance and their failure to move 11 points clear of the reigning champions, though remains adamant that confidence is high.
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"We wanted to win the game and went to Old Trafford to do that. We were eight points ahead of United going into the match and had the chance to make it 11 points. It was a bit of a missed opportunity.
"But we're still top of the league and need to keep the confidence we've had over the last couple of weeks. There's no reason for that to change dramatically. We're still confident we can win games and we have a long way to go."
Vermaelen was a late replacement for Per Mertesacker, who was taken ill before the match, and insists he was fully fit and ready to deputise for the German and make his first Premier League appearance of the season.
"It wasn't hard. I go into every game ready to play," the Belgian added. "I always make sure I'm mentally ready and physically ready, so for me it wasn't difficult.
"I knew it could happen at any moment so I'm always ready. I've been saying it for weeks and months and all of a sudden it happened.