Andy Liddell had put the home side in front with a sweetly-struck free-kick after 26 minutes.
And the game ended on a sour note when Forest's Andrew Impey picked up a second yellow card for getting involved in a fracas in the United penalty area.
Sheffield United boss Neil Warnock:
"You always get your money's worth and you will see some great games at
Bramall Lane before the end of the season.
"Our passing and interchange play was outstanding and I don't think they
could cope with it. Circumstances made it difficult for us that's the best we've
played in a long time.
"The midfield was excellent, Danny Cadamarteri had a great game, Michael
Tonge had an excellent second half, it was just fantastic and I have nothing but
praise for the players."
Nottingham Forest boss Joe Kinnear:
Did not attend the post-match press conference.
Sheff Utd: Kenny, Montgomery, Harley, Bromby, Liddell,
Jagielka, Thirlwell, Quinn, Tonge, Shaw,
Cadamarteri (Lester 90).
Subs Not Used: Gabrieli, Francis, Forte, Ross.
Sent Off: Quinn (42).
Booked: Bromby, Kenny.
Goals: Liddell 26.
Nottm Forest: Gerrard, Louis-Jean, Robertson (Commons 45 (Gardner 90),
Dawson, Morgan, Impey, Evans, Jess (Perch 70), Rogers, Johnson,
Subs Not Used: Bopp, Roche.
Sent Off: Impey (90).
Booked: Impey, Evans, Dawson, Commons.
Goals: Johnson 84.
Ref: G Salisbury (Lancashire).