Iceland midfielder Gunnarsson drove home from the edge of the box in the 70th minute to settle the match after Forest had failed to fully clear a Kadeem Harris cross.
Mark Warburton’s Forest lacked a cutting edge up front, and, not helped by Burton’s win at Birmingham, slipped to 21st in the Sky Bet Championship table – one place and one point above the drop zone.
Warburton needs to find some answers quickly with three games left of the regular season, but Neil Warnock’s Cardiff have no such worries and just about deserved their 16th league win of the campaign.
Peter Whittingham started well on his return to the Cardiff side. His clever through-ball found Kenneth Zohore but the striker dawdled, cut inside, and saw his shot blocked by Daniel Fox.
Whittingham’s undoubted class was again made clear moments later, the midfielder unleashing a trademark left-footed shot from 35 yards which left Jordan Smith’s crossbar rattling.
It was the Bluebirds who held the upper hand, lowly Forest struggling to find an attacking outlet with Jamie Ward isolated up front.
Eric Lichaj and David Vaughan blazed high and wide for the visitors from the edge of the box and Mustapha Carayol went close on two occasions, but the fact neither goalkeeper had a real save to make told the story of a goalless first period.
Forest, after a slow start, had grown into the game in the opening 45 minutes which ended with a brief touchline skirmish between assistant managers Kevin Blackwell and David Weir.
Strikers Zohore and Ward both had chances on the game’s resumption, while Anthony Pilkington bent a free-kick wide for the home team.
Zohore and Carayol remained the men most likely to break the deadlock, the Dane off target again and the Forest winger cutting inside to bring an acrobatic stop from Cardiff goalkeeper Allan McGregor.
That seemed to give Forest belief, but they then quickly fell behind. Harris went down the left, and the ball found its way to Gunnarsson, who took his time and found the bottom corner to finally give the home crowd something to cheer.
Forest introduced forwards Britt Assombalonga and Zach Clough in a bid to get back into the game and they dominated the final 10 minutes.
Substitute Apostolos Vellios hit the bar with a header from Carayol’s cross and Assombalonga should have done better with one chance, but Warburton’s men just could not score.
Cardiff’s Junior Hoilett had a late effort ruled out for offside, but the points were won.
April 17, 2017