Cardiff were infuriated by the decision to disallow Callum Robinson's second-half goal
Mark Hudson suffered his first defeat as Cardiff City interim manager as his team lost at home to the Championship's bottom side Coventry City.
Victor Gyokeres scored from a rebound to give Coventry a half-time lead.
Callum Robinson thought he had equalised after the break but his close-range strike was controversially disallowed for offside.
The same player had a penalty appeal rejected and volleyed over as Cardiff searched in vain for a late leveller.
The end of their three-match unbeaten run under Hudson sees the Bluebirds drop to 16th place in the Championship table, albeit still only four points away from the play-off spots.
Coventry remain at the foot of the table but, with three games in hand over most of their rivals and judging by this performance, that position could soon change.
Before their trip to south Wales, the Sky Blues found themselves six points adrift at the bottom having mustered just one win from their opening 10 fixtures, in which they had scored a joint-division low of eight goals.
They had a glorious opportunity to add to that paltry total in the third minute when Cardiff goalkeeper Ryan Allsop rushed out and made a hash of his clearance.
That left the goal unattended as the ball fell to Gyokeres and, although two Cardiff defenders rushed back to try and cover their wandering keeper, the former Swansea striker still should have scored but instead curled his shot high and wide.
Jolted by that reprieve, the hosts responded with two chances for Robinson, who saw one shot blocked from Ryan Wintle's well-disguised low corner and another drift narrowly wide.
Gyokeres was then presented with an open goal he simply could not miss. Matt Godden's flick set up Jamie Allen for a shot inside the box which Allsop did well to palm away, but only to Gyokeres who tapped in from close range.
Coventry were worthy of their half-time lead, though they were close to losing it five minutes into the second half.
Cardiff thought they had equalised when Robinson finished neatly inside the six-yard box but, after consulting with his assistant, referee Bobby Madley disallowed the goal after judging that Joe Ralls had headed the ball back into the penalty area for Robinson, who was offside.
Bluebirds players and supporters furiously contested the decision, insisting that it was a Coventry player who had headed the ball back into his own area.
They were angered again when Madley ignored Robinson's claims for a penalty after he fell under a challenge from Kyle McFadzean, but those appeals were optimistic at best.
Robinson only had himself to blame when he blazed over from eight yards out and, as Madley blew the final whistle, the only thing louder than the boos from the home crowd were the elated roars of the noisy travelling supporters from Coventry as they savoured three well-earned points.
Cardiff City interim manager Mark Hudson said:
"I think in the first half we weren't at the level we were last week. We started the second half really well and scored a goal which was disallowed.
"I'm still trying to work it out. I've watched it back over and over again. He's onside, they've given it offside because of a rule that the defender isn't in control of the ball but my argument to that is that Robbo [Robinson] was onside throughout that.
"I've spoken to Bobby [Madley]. He says he gave offside because of an action that is a defender not being in control of the ball but the main point is he [Robinson] is not offside at any point in the move.
"That's disappointing but, overall, we didn't work the keeper enough.
Coventry City manager Mark Robins said:
"It was a good result. We started off not great, gave the ball away a bit too much and they've got some pace and power in the team. Thankfully we grew into the game.
"We had a bit of luck with the goal that was disallowed. We got away with that but, other than that, we did OK.
"It was one of those days where, if you're not playing as well as we know we will do at some point, you've got to defend collectively well and generally we did that.
"Although they had quite a bit of possession, this was a battling away performance and thankfully we got the three points. I'm delighted with the three points - they're really important."
- Line-upsMatch StatsLive Text
Line-upsCardiff
Formation 4-3-3
1Allsop22Daley-Campbell38Ng23Kipré37Nkounkou35Rinomhota6Wintle8Ralls11O'Dowda47Robinson29M Harris
- 1Allsop22Daley-CampbellSubstituted forSimpsonat 64'minutes38Ng23Kipré37NkounkouSubstituted forOjoat 71'minutes35RinomhotaSubstituted forSawyersat 64'minutes6Wintle8Ralls11O'DowdaSubstituted forPhilogene-Bidaceat 82'minutes47Robinson29M HarrisBooked at 56minsSubstituted forEteteat 82'minutes
Substitutes
- 9Etete10Ojo16Nelson19Sawyers21Alnwick25Philogene-Bidace26Simpson
Coventry
Formation 3-5-2
13Wilson3Doyle5McFadzean2Panzo23Dabo14Sheaf28Eccles8Allen27Bidwell24Godden17Gyökeres
- 13Wilson3DoyleSubstituted forRoseat 23'minutes5McFadzean2PanzoBooked at 56mins23Dabo14SheafBooked at 48mins28Eccles8AllenSubstituted forPalmerat 75'minutes27BidwellBooked at 90mins24GoddenSubstituted forWaghornat 75'minutes17GyökeresBooked at 40mins
Substitutes
- 1Moore4Rose9Waghorn20Kane30Tavares Desidério32Burroughs45Palmer
Referee:Robert MadleyAttendance:19,861Match StatsHome TeamCardiffAway TeamCoventryPossessionHome53%Away47%ShotsHome15Away11Shots on TargetHome1Away4CornersHome12Away7FoulsHome6Away12Live Text Post update
Match ends, Cardiff City 0, Coventry City 1.
90'+5'Full Time
Second Half ends, Cardiff City 0, Coventry City 1.
90'+5'Post update
Attempt missed. Perry Ng (Cardiff City) header from the centre of the box misses to the right. Assisted by Joe Ralls with a cross following a set piece situation.
90'+5'Booking
Jake Bidwell (Coventry City) is shown the yellow card for a bad foul.
90'+4'Post update
Kion Etete (Cardiff City) wins a free kick on the right wing.
90'+4'Post update
Foul by Jake Bidwell (Coventry City).
90'+2'Post update
Attempt missed. Romaine Sawyers (Cardiff City) right footed shot from the left side of the box misses to the left following a corner.
90'+2'Post update
Corner, Cardiff City. Conceded by Josh Eccles.
90'Post update
Ryan Wintle (Cardiff City) wins a free kick in the attacking half.
90'Post update
Foul by Martyn Waghorn (Coventry City).
88'Post update
Hand ball by Kion Etete (Cardiff City).
88'Post update
Jack Simpson (Cardiff City) wins a free kick in the defensive half.
88'Post update
Foul by Martyn Waghorn (Coventry City).
87'Post update
Corner, Coventry City. Conceded by Ryan Allsop.
87'Post update
Attempt saved. Jake Bidwell (Coventry City) header from the centre of the box is saved in the top centre of the goal. Assisted by Martyn Waghorn.
85'Post update
Offside, Coventry City. Michael Rose tries a through ball, but Martyn Waghorn is caught offside.
84'Post update
Attempt missed. Callum Robinson (Cardiff City) right footed shot from the left side of the box is too high following a corner.
84'Post update
Attempt blocked. Jack Simpson (Cardiff City) header from the centre of the box is blocked. Assisted by Joe Ralls with a cross.
83'Post update
Corner, Cardiff City. Conceded by Fankaty Dabo.
82'Post update
Foul by Kasey Palmer (Coventry City).
Page 1 of 6rewindpreviousNavigate to the next pagenextNavigate to the last pageforward
Source: bbc.com