United conceded two second half goals as they fell to defeat at Chesterfield on Tuesday evening, after going down to ten men in the first half when Elliot Embleton was sent off.
Mark Hughes made three changes from the defeat at Doncaster on Saturday, with Georgie Kelly, Charlie McArthur and Sean Fusire replacing Stephen Wearne, Cameron Harper and Joe Bevan.
A further change was made ahead of kick-off when Matty Dennis pulled out during the warm-up. Joe Hugill took his place in the starting line-up and Cedwyn Scott came onto the bench.
Georgie Kelly had the first effort of note with six minutes on the clock when he picked up a misplaced pass from Jamie Grimes, but his effort from 30 yards out lacked power and Boot held it in the Chesterfield goal.
Gabe Breeze was called into action after 15 minutes when Ollie Banks spun and shot from the edge of the box, the keeper tipped the shot over the bar then punched away the resultant corner.
Banks went close again ten minutes later when he got a glancing header on a corner, but it flew just past the post.
Chesterfield should have been ahead shortly afterwards when Grigg put a ball into the box, but Dobra's effort from the penalty spot went wide.
United were dealt a big blow five minutes before the break when Elliot Embleton was sent-off for a foul on Dobra. The fourth official seemed to advise the referee on the decision after a long delay.
HALF-TIME: Chesterfield 0-0 United
United threw bodies in the way in the first minute of the second half as Chesterfield looked to start strongly, but Breeze and his defence stood up to block a number of shots after a scramble in the box.
Breeze was called into action again shortly afterwards when he had to tip a Dobra shot over the bar. Dobra had another effort from the resulting corner which Breeze was also equal to before he made his third save in quick succession as Olakigbe got a shot off from inside the box.
Grigg should have put the hosts ahead with an hour on the clock but he could only direct Banks' wicked ball into the box over the bar.
Charlie McArthur made a great block to prevent Grigg from scoring three minutes later, the young defender throwing himself in front of a powerful effort inside the box.
Breeze then pulled off another fantastic save as Mandeville was free at the back stick, palming his effort behind for a corner.
The home side broke the deadlock with 73 minutes on the clock, a Jenson Metcalfe shot was blocked but the rebound fell nicely for Liam Mandeville to slot home.
Madden made it two shortly after he came onto the pitch after he was the quickest to react to a shot which came back off the bar to head home.
United pulled a goal back on 88 minutes after Joe Hugill calmly finished past Boot in the Chesterfield goal.
The Blues continued to push forward and Joe Bevan earned a corner. Callum Guy's ball was headed straight at the keeper by Ben Barclay.
FULL-TIME: Chesterfield 2-1 United
Teams:
Chesterfield - Boot, Grimes, Mandeville, Grigg (Madden 74), Fleck (Oldaker 74), Dobra (Jacobs 83), Gordon, Palmer, Metcalfe, Banks (Colclough 83), Olakigbe (Duffy 83).
Unused subs - Thompson, Pepple.
United - Breeze, Davies, Thomas, Lavelle (C) (Ellis 45 +4), Kelly (Bevan 46), Vela (Barclay 76), Hugill, McArthur, Harris, Whelan (Guy 76), Fusire (Embleton 29).
Unused subs - Lewis, Scott.
Goals:
Chesterfield - Mandeville (73)
United - Hugill (89)
Yellow cards:
Chesterfield - N/A
United - Hugill (70), Thomas (90), Hodges (90)
Red cards:
Chesterfield - N/A
United - Embleton (41)
Match officials:
Referee - Andrew Humphries
Assistant Referee 1 - Andrew Ellis
Assistant Referee 2 - Keiran Forrest
Fourth Official - Joseph Pettitt
Attendance:
7,508 (309 away)
