Arsene Wenger's side pressed late in the match and eventually got their equaliser when Welbeck struck in the 91st minute, but the England man was only partially content with his stoppage-time leveller.
"It was bittersweet because we started the game well," Welbeck told the club's official website. "They got the early goal and made it difficult for us because they just sat back. I was pleased to get a goal but disappointed not to get the three points.
"There's different ways you can look it at because they've been working hard all game, they maybe got a bit tired towards the end.
"You don't see those sort of things on the pitch but being on the pitch makes things more difficult. We need to see how we can evaluate it from there."
Arsenal are sixth in the Premier League table, with 11 points from eight games this season.