Kidderminster Harriers had Anthony Malbon stretchered off as they missed out on the Blue Square Bet Premier play-offs for the second year running.
Harriers needed to win and hope that rivals Luton slipped up at Fleetwood.
But Lee Vaughan was sent off just after the break for an elbow on Matt Rhead.
Five minutes later, the Stags cashed in when Lee Stevenson fired home a low shot before Louis Briscoe wrapped it up, heading home Andy Todd's cross, Matt Green adding a late third.
Briscoe - sent off against Kidderminster earlier in the season - was the man involved in the serious incident involving young striker Malbon.
The Stags striker was booked for his heavy challenge on Malbon which left his opponent knocked out cold and having to undergo nine minutes of treatment.
He was stretchered off before being airlifted to hospital by helicopter after the game, suffering from suspected concussion.
Referee Jez Simpson blew for full-time a few minutes early to allow Malbon to be picked up from the Aggborough pitch by the air ambulance.
Briscoe, perhaps fortunate to be allowed to stay on the pitch, hit third-placed Mansfield's second before Ryan Rowe hit the post for the home side.
Green completed Harriers' misery when he fired home a low shot on 86 minutes.
Harriers' hopes always looked bleak once news had filtered though of Luton's early goal at Highbury.
But defeat, triggered by Vaughan's second dismissal of the season, coupled with Luton's eventual 2-0 victory at Fleetwood, ensures that Steve Burr's men finished sixth for the second year running.
VIEW FROM THE TRAINING GROUND
Kidderminster assistant manager Gary Whild told BBC Hereford & Worcester:
"Losing is a disappointment but overall, across the whole season, to finish sixth again is a fantastic achievement.
"You only have to look at the clubs in the play-offs, they're massive clubs. For us to be taking them all the way, with our resources, the gaffer has done an absolutely fantastic job.
"It's great to come as far as we have with a young bunch of players who'll be a lot better for the experience they've had this season."
Mansfield Town manager Paul Cox told BBC Radio Nottingham:
"Anybody that's picked to put a Mansfield Town shirt on now is expected to have a winning mentality.
"We want a squad of 22 players who're all chomping at the bit to get in the first 11 and nobody in the first 11 can rest on their laurels.
"The lads out there today were a different level, even right at the end when they could have took their foot off the pedal. But we kept going, It's just a tremendous group to work with and manage."