The former Barcelona midfielder had spent most of previous day in meetings with club officials
Some Arsenal fans, disgruntled by the club's 12-year wait for a Premier League trophy, held up protest boards in the 12th minute and also with 12 minutes of the match left.
Yet others in the crowd expressed their disapproval at the disruption and Welbeck's 59th-minute strike, four minutes after he came on, lifted the mood in the Emirates Stadium.
Norwich, who were the only side of the three battling to avoid relegation not to pick up any points on Saturday, remain deep in trouble in 19th place, two points from safety.