Robert Earnshaw scored his 150th league goal to put Forest ahead in the fourth minute of Tuesday night's Championship clash at The City Ground but the visitors were well in the game until the dismissal of Darius Henderson 40 seconds into the second half.
The 1-0 victory, which comes after back-to-back away defeats, leaves Forest just two points off West Brom and Newcastle who share the lead at the top of the table, but Billy Davies is taking nothing for granted.
"Three defeats in 26 games I think it is," he said. "It is a fantastic record, but there'll be twists and turns between now and the end.
"We don't get too carried away when we win, and we don't get too down when we get beaten.
"We're not going to win every game and we're going to have difficult moments, but I'm very concerned about tired legs and have been for many weeks.
"We were tired at Coventry, we were tired at Derby, we were tired at Doncaster and it is a big, big concern.
"I didn't see the sending off and I say that genuinely. I don't know what happened."
For Davies - and the majority of a 22,000 crowd - the game could not have got off to a better start as he was rewarded for a switch in selection as the recalled Paul Anderson and Earnshaw combined to open the scoring after just three minutes with a close range effort following Radoslaw Majewski's in-swinging corner.
The early setback seemed to knock the Blades and they struggled to gain composure as Forest threatened to double their lead with Cohen, Anderson and Majewski all going close.
If Kevin Blackwell was hoping for a change in fortunes for his side after the break, he was to be sorely disappointed as Henderson rendered the comeback mission impossible as he appeared to elbow Forest's Kevin Wilson off the ball less than a minute into the action.
From then on, the 10 men worked hard with Mark Yeates twice going close to equalising but Forest were always comfortable and were unlucky themselves not to double their lead with a series of chances throughout the second period with Nathan Tyson most notably going close.
It leaves the Blades with just one win from six, but Blackwell refused to criticise his players for their effort - and found it hard to accept the red card was justified.
He said: "I spoke to Darius [Henderson] - he feels hard done by that's for sure, but without seeing it I can't comment.
"As a manager we're not allowed to speak our minds, because you get done for berating officials.
"I want to talk about the officials, but I can't.
"It was a sloppy goal, but from that early setback, I thought the lads responded well."
Source: Team Talk