Oxford United staged a smash and grab raid to nick the points at highly-fancied Lincoln.
United, who were beaten to a play-off place by the Red Imps on the final day of last season, were quick to make their mark, new striker Julian Alsop narrowly missing the target with a third minute header as Lincoln were immediately forced back.
United's Steve Basham made no mistake three minutes later when he netted the easiest of goals after Lincoln keeper Andy Marriott dropped a cross.
Derek Townsley went close to increasing United's lead before Lincoln put their first attack together in the 18th minute.
Close season signing Richard Liburd fought his way down the right flank but from his cross Simon Yeo headed wide.
Yeo, a hero for Lincoln last season, played little further part in the action after being red carded for earning two bookings in the opening 33 minutes.
Lincoln battled hard despite being a man short but Oxford always looked more likely to add to their lead.
They should have scored again midway through the second half when the lively Alsop set up a superb pass for Townsley only for the midfielder to shoot wide of an open goal.
Lincoln substitute Ellis Remy, signed in the week from Hastings, livened things up and twice went close in the closing stages.
But Oxford finished on top with Paul Wanless only denied a debut goal by an excellent save from Marriott.
Oxford manager Ian Atkins said after the match: "We were always in control but we were a bit too elaborate at times.
“It was just disappointing that we didn't manage to get a second goal but Lincoln is never an easy place to come to." Lincoln manager Keith Alexander said: "It was always going to be difficult once we were a man down. I was very disappointed with the sending off.
“I am not making excuses but I thought we deserved better than that against one of the better teams in the division."