Michail Antonio’s cool finish proved to be noting more than a late consolation after goals from Kenwyne Jones and Joe Mason put the Bluebirds 2-0 up.
Dougie Freedman made two changes to the side that was pegged back late on at Bolton.
The manager said Chris Burke and David Vaughan ‘turned the game’ after coming on in the second half at the Macron Stadium, and this afternoon they were rewarded with a place in the starting line up.
There were home debuts for left back Daniel Pinillos and central midfielder Kyle Ebecilio, while Tyler Walker was chosen to lead the line ahead of substitute Dexter Blackstock.
It was another young squad for Forest as Dimitar Evtimov, Oliver Burke, Jorge Grant, academy striker Gerry McDonagh and Osborn joined Blackstock and Kelvin Wilson on the bench.
The first half-chance of the match fell to Burke, who looked well placed to turn the ball home from Antonio’s cross only for Fabio Da Silva to nip in and send it behind for a corner.
The resultant delivery caused panic in the Cardiff area and the ball eventually dropped for Ebecilio. The Dutchman could only curl it high over the bar.
Dorus de Vries was tested twice as Cardiff looked to assert their authority. He made comfortable saves from Anthony Pilkington, who had cut in from the right, and Joe Mason, whose shot at the end of a speedy counter attack was straight at the keeper.
But Forest did find themselves a goal behind on 23 minutes. Eric Lichaj misjudged a defensive header, presenting Peter Whittingham with the ball in a good crossing position. The midfielder’s delivery was pinpoint and Jones’ execution was superb, heading the ball low to de Vries’ right and into the net.
There was further frustration for Forest shortly after play resumed when a Cardiff defender nipped in ahead of Walker to turn behind Antonio’s low cross from the left.
And The Reds had their hearts in their mouths moments later when Joe Mason stayed onside to receive Fabio’s neat pass in the area. Mason was stood up by Mills but he managed to trick his way past the defender, working a shooting position from a tight angle. De Vries positioned himself at his near post to push away the shot.
Cardiff keeper David Marshall was called upon for the first time on 35 minutes. Vaughan robbed Whittingham of possession in the middle and offloaded the ball to Walker, who had made a run to his left. The young striker cut inside on his right foot and unleashed a powerful effort at goal from the edge of the area. Marshall dived to his left to push the ball away.
Three minutes later, more excellent ball-winning work by Vaughan presented himself with the opportunity to supply Walker once more. Vaughan’s through ball was beautifully weighted but Matthew Connolly had enough pace to make a last-ditch challenge, nudging the ball to safety.
Forest’s pressure continued as half-time neared, Mills sending the ball wide with a first-time strike from a corner and Burke missing the target after twisting his way past Connolly.
The Reds were unable to level the scores before the break, however, and Freedman saw fit to make a change during the interval - sending on Osborn in place of Ebecilio.
And the substitute was involved almost immediately, receiving a pass from Antonio on the edge of the area. He turned towards goal but snatched at his shot, sending it harmlessly wide.
Despite those encouraging signs, Forest found themselves 2-0 down on 49 minutes.
Pilkington’s effort from just inside the area looked like it was curling into the top corner, but Mason ran across the path of the ball to nod it past the helpless de Vries.
Blackstock replaced Burke just before the hour with Walker moving out to the right.
Antonio was also playing in an advanced position, and he attempted an audacious effort after Blackstock’s flick-on bounced to him 35 yards out. He struck the ball first time, sending it whistling wide of Marshall’s post.
But it was a more conventional effort that had Marshall worried moments later, Antonio scampering into the box and seeing his low, left-footed shot well saved by the keeper.
Forest were cranking up the pressure and two substitutes combined to test Marshall once more on 65 minutes. Blackstock’s aerial prowess was again evident as he nodded the ball down for Osborn on the edge of the area. The midfielder took his shot on the bounce but couldn’t dip the ball over Marshall.
It was transpiring to be a busy second half for Marshall, who denied Walker at his near post with around 20 minutes remaining.
The youngster was proving himself as a considerable threat and he did well to meet Antonio’s cross at the back post on 75 minutes. Closely marked, the odds were always stacked against him and he could only head the ball wide.
And Walker caused yet more panic shortly afterwards, dribbling his way into the area and forcing a combination of defender and goalkeeper to turn the ball behind.
That was to be Walker’s final act as he was replaced by his former Under 18s team-mate McDonagh.
The match looked like it may have been ebbing away from Forest until the 86th minute, when Blackstock’s flick on split the Cardiff defence, sending Antonio into the gap. He rode a challenge in the area before coolly slotting the ball low past Marshall.
Forest were given six minutes of injury time to try and find an equaliser, but the next chance fell to Cardiff. Substitute Sammy Ameobi got away from Hobbs in a wide position and rolled the ball to the unmarked Mason eight yards out. The striker’s touch failed him and de Vries claimed the ball.
With a minute and a half of injury time to go, Antonio picked the ball up in midfield and worked his way into a crossing position. He drifted the ball to the back post and Mills stretched himself to meet it but, agonisingly, he was unable to make contact.
And that proved to be the final action as The Reds were beaten 2-1.
Forest: De Vries, Lichaj, Mills (c) Hobbs, Pinillos, Mancienne, C Burke (Blackstock 59'), Ebecilio (Osborn 46'), Vaughan, Antonio, Walker (McDonagh 80')
Subs not used: Evtimov, Grant, O. Burke, Wilson
Goal: Antonio 86'
: Marshall (c), Peltier, Morrison, Connolly, Fabio (Cardiff
Malone 80'), Dikgacoi, Whittingham, Ralls, Pilkington (Noone 90'), Jones (Ameobi 69'), Mason
Subs not used: Moore, Manga, O'Keefe, Revell
Goals: Jones 23', Mason 49'
Bookings: Ralls 20', Fabio 33', Ameobi 84', Pilkington 90'
Referee: Oliver Langford
Attendance: 18,762 (660 away)