Results elsewhere in Sky Bet League Two confirmed the U’s position in the Football League with two games of the season remaining, despite a frustrating 2-1 defeat at Forest Green Rovers on Easter Monday.
United were undone by a pair of corners in each half of the game, with Gunning and Doidge doing the damage to resign Paul Lewis’ fine strike midway through the second half as a consolation goal.
Colin Calderwood made six changes from the Good Friday clash with Swindon Town, as Leon Davies, Louis John, Harry Darling and Jake Carroll all stepped into the side as Greg Taylor moved into midfield, whilst Paul Lewis and Hayden Coulson returned to the starting eleven further up the field.
Louis John was presented an early opportunity to carry the ball forward for the U’s, and the centre back accepted Forest Green’s invite before letting fire on a venomous strike from 40 yards which James Montgomery did well to parry away with both gloves.
Rovers danger man Christian Doidge arrived late at the U’s back post from the first corner of the game on seven minutes but the striker glanced his header wide of the mark.
Despite the game settling into a steady pace with both sides sharing equal spells of possession, the U’s were indeed unlocked by a Forest Green set piece when Gavin Gunning got across the front post and steered a header into the far bottom corner on 24 minutes.
Doidge threatened to get in behind the U’s back four six minutes later but was denied the chance of a one-on-one with Dimitar Mitov with an excellent covering interception by Jake Carroll.
Dayle Grubb’s looping free kick moments before the break looked to have doubled United’s task but the midfielder’s effort from wide on the left cracked the frame of the goal having beaten Mitov, and the U’s were able to clear the rebound to keep the deficit at just one.
With the game still well within United’s grasp after half time, Colin Calderwood made a pair of changes to provide United extra fire power heading into the final half an hour as Jevani Brown and Jabo Ibehre took to the field.
And with the match asking for someone to take it by the scruff of the neck from a U’s perspective, up stepped Paul Lewis who knocked the ball out of his feet and rifled home a low shot from 35 yards that zipped past Montgomery to level the scores on 66 minutes.
Rovers regained their lead ten minutes later however when Christian Doidge showed his predatory instincts to react quickest to a loose ball inside the U’s six yard, after Mitov had initially saved Reece Brown’s effort at goal from another Forest Green corner.
Youngster Tom Knowles replaced Greg Taylor for the final six minutes of the game, with the U’s centre back hobbling off after an earlier collision. But the U’s couldn’t muster an opportunity of note to draw level for a second occasion.
Forest Green Rovers: Montgomery, Shephard, Rawson, Winchester, Grubb, Doidge, Brown (Digby, 90 minss), Gunning, McGinley, Mills, Mondal (Reid, 83 mins)
Cambridge United: Mitov, Davies (Ibehre, 61 mins), Taylor (Knowles, 84 mins), John, Darling, Carroll, Deegan, Lewis, Amoo (Brown, 61 mins), Coulson, Hepburn-Murphy
Attendance: 2,699 (232)