Cardiff boosted their hopes of a Premier League great escape with a vital 2-0 victory which increases the relegation fears of fellow strugglers Brighton.
Toothless Brighton, who have managed just two top-flight goals at the Amex Stadium in 2019, once again struggled to create as they suffered a fourth successive league loss.
Glenn Murray headed against the woodwork in stoppage time but the Seagulls offered little in attack and remain anxiously looking over their shoulders.
With title-chasing Liverpool and Manchester United still to come this season, anything but a win on the south coast would have left the visitors with an improbable chance of avoiding an immediate return to the Sky Bet Championship.
Bluebirds manager Neil Warnock reacted to Saturday’s defeat at Burnley by making three changes, including recalling attacking duo Mendez-Laing and Oumar Niasse.
That decision was rewarded within 22 minutes as Mendez-Laing drove forward on the counter-attack, exchanged passes with Junior Hoilett and proceeded to curl a superb strike into the top right corner from 20 yards.
Brighton, keen to make up for their 5-0 weekend thrashing by Bournemouth, had begun the game the brighter of the two teams, with Solly March rippling the side-netting inside two minutes and City goalkeeper Neil Etheridge scrambling the ball away from the onrushing Murray.
Referee Andre Marriner then waved away penalty appeals when Lewis Dunk appeared to be wrestled to the ground by Bruno Ecuele Manga following a Pascal Gross free-kick.
The opening goal increased the tension among home fans who have seen their side collect just four points on home soil this year.
They initially greeted the half-time whistle with jeers, before quickly turning their understandable frustration to encouragement and applauding their below-par team off the pitch.
However, the brief moment of optimism was soon quelled as the visitors doubled their advantage five minutes after the restart.
Spanish midfielder Victor Camarasa delivered an inviting free-kick deep into the Albion area where centre-back Morrison escaped the attentions of Seagulls striker Murray to powerfully head home his first goal in almost a year in front of the travelling support.
Brighton boss Chris Hughton introduced Florin Andone and Jose Izquierdo from the bench in the hope of inspiring a fightback.
Colombia international Izquierdo almost had an immediate impact when he laid the ball off the ball off for Murray to smash narrowly over the crossbar from 18 yards.
Albion, who still have a game in hand on Cardiff and a superior goal difference, have to face top-four hopefuls Tottenham and Arsenal as well as champions Manchester City during a tough run-in.
As the clock ticked down the Seagulls showed little sign of breaching the away side’s resilient defensive line.
Romania forward Andone threatened to halve the deficit only to be thwarted by a fine last-ditch block from the impressive Morrison.
Murray then nodded March’s right-wing cross against the right post late on, leaving the vocal away following to toast only a third away win of the season which could have a major bearing on the battle for survival.