OXFORD United’s play-off hopes were snuffed out with a defeat in their final game of the season.
Marc Richards’ shot put the hosts in front at half-time after an evenly contested opening 45 minutes.
United were spurred on by news rivals Crewe Alexandra were losing, but their commitment to attack saw them caught out midway through the second half, when Sean Rigg struck a second goal on the break.
It gave the U’s a mountain to climb and they could not find a way back into the contest, conceding a third goal to Ben Williamson in stoppage time, as their season petered out with a seventh game without a win.
Manager Chris Wilder made four changes in an unfamiliar starting line-up, with Damian Martinez, Tony Capaldi, Peter Leven and Tom Craddock coming into the side.
It meant a change of system, switching from 4-3-3 to a 4-4-1-1, with Craddock playing in behind Jon-Paul Pittman, who had the first sight of goal.
Just two minutes were on the clock when the striker cut in from the right flank and arrowed a low shot from 20 yards which beat Vale goalkeeper Stuart Tomlinson but slipped past the post.
Craddock had the next clear opening, on 19 minutes, when he was put through by Andy Whing, but the striker delayed his shot long enough for Joe Davis to recover and block.
Vale had plenty of the ball but Martinez, signed on loan from Arsenal yesterday, was untested until the 37th minute.
Rigg, who looked lively on the left flank, got to the byline and hung up a cross to the back post, which Tom Pope headed straight at the Argentinian goalkeeper.
Martinez was beaten four minutes later, when Marc Richards pounced on United skipper Jake Wright’s back header, nipping in to flick a finish into the net.
Despite the scoreline, United were given added impetus at the break with the news play-off rivals Crewe Alexandra were 2-1 behind at home to Aldershot.
In response Adam Chapman, Scott Rendell and Oli Johnson were all brought on as the U’s adopted their more familiar 4-3-3 formation.
It almost made an immediate impact, with Leven playing in Chapman on the counter-attack, but the midfielder’s attempted chip was easily caught by Tomlinson.
The changes transformed the tempo of the game, with United on top but leaving gaps at the back for Vale to exploit on the counter-attack.
Richards nearly made it 2-0 just before the hour, but Capaldi did brilliantly to slide in and deflect the close range shot over the crossbar.
The game was wide open and United needed a brilliant save from Martinez to stay in the game, with the goalkeeper tipping Tom Pope’s header over the bar.
From the resulting corner Vale had two efforts blocked on the line, while Pope hit the post.
A goal for one of the sides seemed inevitable, and it arrived on 69 minutes when Vale doubled their advantage.
The hosts sprung on the counter-attack, leaving Wright to face two attackers. Rigg opted to the chance on himself, going past the defender’s challenge and lashing a shot past Martinez.
United continued to attack, but had little joy until Pittman headed into the net six minutes from time. The celebrations were short-lived, with the referre ruling the goal out for a push from the striker on his marker.
Vale ran down the clock with ease and rubbed salt into the visitors’ wounds when Ben Williamson struck a third goal in the final minute.
Attendance: 5,621 (886 visitors).
Oxford Utd: Martinez, Batt, Duberry, Wright, Davis (Rendell 46), Hall, Whing (Chapman 46), Leven, Capaldi, Craddock (Johnson 49), Pittman.
Substitutes: Crocombe, Montano.