Rory Gaffney was the Rovers hero with two second-half goals
Derry City's League of Ireland hopes suffered a major blow as Shamrock Rovers took a significant step towards regaining the title with a 2-0 win at Tallaght Stadium.
Going into Sunday's game - which was rescheduled from Friday because of Rovers' European campaign - the Candystripes aimed to keep the pressure on the leaders after second-placed Bohemians fell to a home defeat by Drogheda United on Friday night.
But after a promising first-half showing, Derry succumbed to a double from Rovers frontman Rory Gaffney, who struck in the 47th and 65th minutes to push Stephen Bradley's side 10 points clear of Bohs at the top.
Derry - who had defender Alex Bannon sent off late on - are a point further adrift in third and are now winless in their past 10 games against Rovers, stretching back to March 2023.
More significantly, a ninth defeat of the season seriously dampens Tiernan Lynch's hopes of delivering Derry's first title since 1997 in his first season in charge.
"We just didn't cope after we conceded," said Lynch.
"And we needed to dust ourselves down, get a hold of the game and slow things down to get a foothold but we conceded a second goal.
"Goals change games and tonight we weren't good enough in our own box. This game is all about both boxes, taking your chances when they come and making sure you defend and unfortunately we didn't do that tonight."
Tiernan Lynch (right) can still claim silverware in his first season as Derry boss in the FAI Cup
In a frustrating night for the Foylesiders, they failed to capitalise while on top. After a bright Rovers start - which included former Derry attacker Aaron McEneff firing over - Michael Duffy spurned the visitors' biggest opportunity when he struck the post after being picked out by Sadou Diallo.
Former Dundalk winger Duffy had another opening when he beat Rovers defender Roberto Lopes before firing wide.
After a quiet opening half, Rovers quickly took control after the restart with Gaffney supplying the finishing touch for the opener after fine work from Joshua Honohan down the left wing.
With Derry rattled, Rovers nearly doubled their lead moments later when Connor Malley - who replaced McEneff at the break - smashed Brian Maher's crossbar.
The cushion Rovers craved, however, was secured by Gaffney, who turned sharply on to his left foot to beat Bannon before rifling a shot beyond Maher.
With Rovers in control, Derry's woes were compounded when Bannon was dismissed after a foul on Honohan earned the Scottish defender a second yellow card.
"The big thing probably with us is there's been a lack of consistency in what we're doing," added Lynch.
"Not a lack of effort or commitment, great bunch of boys working really hard, but a lack of consistency and we need to find consistency."
After thrashing Waterford 7-2 four weeks ago, Derry have picked up just one point from games against Sligo Rovers, Bohemians and Rovers, who look well-placed to regain the title they relinquished to Shelbourne last season.
Lynch's side are next in action at home to struggling Cork City on Friday (19:45 BST), while Rovers travel to Kosovo to face Ballkani in the third round of Uefa Conference League qualifying on Thursday (19:30).
