Ollie Palmer’s close-range header 12 minutes from time saw the Wanderers beaten 1-0 at Adams Park.
Palmer made no mistake from four yards after John Dempster’s header had crashed back off the crossbar, and despite late pressure the Blues failed to test Alan Marriott in the Mansfield goal.
In came Gary Doherty, Nick Arnold, Matt Spring, Jo Kuffour and McClure with Leon Johnson, Stuart Lewis, Sam Wood, Dean Morgan and Jon-Paul Pittman the men making way.
Blues started well and Paris Cowan-Hall was picked out by Arnold at the near post, but he didn’t get enough on an attempted flick to worry Alan Marriott. Anthony Stewart then saw a shot blocked after the visitors failed to clear their lines.
However, it was the Stags who came closest to breaking deadlock early on when James Jennings’ dipping volley was superbly tipped over the bar by Matt Ingram in the 10th minute.
McClure was inches away from opening the scoring in the 20th but Arnold’s fine cross from the right just eluded the frontman after Kuffour had picked out the Reading loanee with a pinpoint crossfield pass.
Sam Clucas headed wide for Mansfield after a free-kick was nodded back across goal by Calvin Andrew and the striker went closer himself just past the half-hour mark when he hooked a volley narrowly off target from the edge of the area.
The best chance of the first half was Wanderers’ and it came eight minutes before the break. Spring played the ball down the left and Cowan-Hall did well to dispossess Lee Beevers near the byline before cutting back for Scowen, only for the midfielder’s effort to be kept out by Marriott.
The lively Cowan-Hall saw his drilled effort parried away by Marriott with three minutes of the half remaining and Arnold fired high over the bar from Spring’s corner in injury-time.
Mansfield were fast out of the traps after the restart and Ingram saved from Jennings before McCoy threw his body in the way of the rebound.
Ainsworth made his first change on the 56th minute introducing Morgan in place of McClure, and Blues’ boss was forced into a second swap 10 minutes when Cowan-Hall was stretchered off holding his knee to be replaced by Wood.
Morgan’s cross eluded everyone after the forward had linked up with Kuffour, but the Wanderers were struggling to break through a solid defence.
Ainsworth made his final substitution with 14 minutes remaining, bringing on Max Kretzschmar for Arnold, but it was the visitors who took the lead two minutes later.
Blues failed to deal with a free-kick from the right and John Dempster crashed a header against the bar, the rebound fell kindly for the visitors and Ollie Palmer scrambled in from close-range.
The visitors should have wrapped it up five minutes from time when a hopeful through ball sent Palmer through on goal, but Ingram narrowed the angle well to make a smart stop.
Kuffour had a great chance to level with time running out when he collected Morgan’s left-footed cross and turned his man, only to drag wide of the far post from six yards.
Morgan saw a hooked effort comfortably saved by Marriott as the Chairboys pushed forward before Kretzschmar got on the end of Kuffour’s fizzed-in cross, but couldn’t divert the ball goalwards.
Wanderers: Ingram, McCoy, Dunne, Stewart, Doherty, Arnold (Kretzschmar 76), Spring, Scowen, Cowan-Hall (Wood 66), McClure (Morgan 56), Kuffour.
Subs: Harrison, Johnson, Pittman, Craig.
Mansfield: Marriott, Sutton, Beevers, Dempster, Riley, Clements, Clucas (Palmer 68), McGuire, Jennings, Hutchinson (Howell 90), Andrew (Rhead 74).
Subs: Mitchell, Stevenson, Tafazolli, Meikle.
Attendance: 3,352 (251 Mansfield)