Danny Mandroiu's 67th-minute strike finally broke Dundalk’s resistance at Tallaght Stadium as Shamrock Rovers kept up the pressure on Derry City at the top of the SSE Airtricity League table with a huge three points.
Stephen Bradley’s side dominated throughout this game but struggled to break down a stubborn opposition until the former Bohs player latched onto a Jack Byrne pass to decide the game midway through the second half.
Stephen O’Donnell had set up the frustrate the home side and it worked for the most part, but they were all too often guilty of creating problems for themselves with Brian Gartland caught out for pace for the winner before being sent off for a second bookable offence three minutes from time.
The visitors made five changes from the side that beat Sligo Rovers on Friday night with big names such as Andy Boyle, Steven Bradley and Patrick Hoban dropping to the bench.
That saw Daniel Kelly deployed up front and he almost gave the Louth men a dream start when he headed against the crossbar inside the opening four minutes after Rovers failed to deal with a superb in-swinging free-kick from Keith Ward.
The home side soon began to turn the screw after that with Nathan Shepperd called into action for the first time on 11 minutes when he went full stretch to his left to keep out Sean Hoare's header from Byrne’s corner.
Dundalk then had another half chance two minutes later after Lee Grace gifted possession to Joe Adams. The Welsh under-21 winger immediately picked out Greg Sloggett who drove at the Rovers defence before cutting onto his weaker left foot, but a deflection took much of the sting off the shot and it was comfortable for Alan Mannus to deal with in the end.
The Hoops fans thought their side had found the breakthrough on 19 minutes. Aaron Greene slipped Sean Gannon in on the right and after his shot was parried by Shepperd the rebound fell to Dylan Watts who pulled his effort just wide of the far post.
Mandriou then went close twice in quick succession either side of the half hour mark - firstly firing just wide from 30 yards out before cutting past Gartland to get a shot away from the left-hand corner of the penalty area which flashed just over.
Dundalk then had another chance on 37 minutes when Ward’s pass was stepped over by Greg Sloggett, allowing Daniel Kelly to open up his body and get a shot away at the edge of the six-yard box but Mannus denied him with his legs.
Byrne then had an effort straight at Shepperd within five minutes of the restart but despite plenty of further pressure it would take until the 67th minute for them to really threaten again.
When they did, they found the breakthrough as Byrne’s through ball saw Mandriou race past a statuesque Dundalk defence before slotting past Shepperd in front of the South Stand.
Substitute Aidomo Emakhu then had a great chance to double his side’s lead after breaking clear on the right on 73 minutes but he could only pull his effort across the face of goal and wide in the end.
Mandroiu would sting the palms of Shepperd nine minutes later after Rovers looked to break as Dundalk threw caution to the wind.
Their hopes of getting anything from the game were severely dented three minutes from time when Gartland was sent off by referee Ray Matthews for a second bookable offence after a foul on Emakhu.
Substitute Bradley had a last-gasp chance to rescue something for the visitors when Darragh Leahy’s long throw dropped to him in the box but he failed to get the purchase on his effort to deny his namesake in the Rovers dugout from celebrating a big three points.
Shamrock Rovers: Alan Mannus; Sean Hoare, Roberto Lopes, Lee Grace; Sean Gannon (Andy Lyons 62), Dylan Watts (Richie Towell 78), Gary O’Neill, Neil Farrugia (Barry Cotter 61); Jack Byrne (Chris McCann 85), Aaron Greene (Aidomo Emakhu 62), Danny Mandroiu.
Dundalk: Nathan Shepperd; Lewis Macari, Brian Gartland, Mark Connolly, Darragh Leahy; Sam Bone, Paul Doyle (Ryan O’Kane 79); Greg Sloggett (Patrick Hoban 72), Keith Ward (David McMillan 72), Joe Adams (Steven Bradley 62); Daniel Kelly (John Martin 79).
Referee: Ray Matthews (Westmeath).