Grimsby Town lost for the first time this season as they were narrowly beaten by Forest Green Rovers at The New Lawn.
Substitute Junior Mondal grabbed the only goal of the game 14 minutes from time to ensure the points stayed in Gloucestershire.
The Mariners created chances and deserved to take something from the game but were unable to convert any of those opportunities, bringing to an end their unbeaten opening to the campaign.
Town made two changes to the team that drew with Bradford City in their previous league game as new signning Luke Waterfall came in for the injured Ludvig Ohman at centre-back and Moses Ogbu replaced Ahkeem Rose in attack.
James McKeown began in goal, with Elliott Hewitt, Harry Davis, Waterfall and Luke Hendrie in defence.
Harry Clifton, Jake Hessenthaler and Elliott Whitehouse were the midfielders, with Matt Green, James Hanson and Ogbu forming the attack.
The Grimsby substitutes were Sam Russell, Liam Gibson, Jordan Cook, Max Wright, Charles Vernam, Sebastian Ring and Mattie Pollock.
Forest Green came into the game having also taken four points from their opening two league fixtures and having progressed into the second round of the Carabao Cup with a penalty shoot-out victory at Charlton on Tuesday.
Town's first attack of note saw Hewitt send a cross into the penalty area but the ball was cleared after it had been headed on by Hanson.
Another half-chance came on 10 minutes when Hanson knocked the ball down for Waterfall but his ball across goal was cleared from danger.
A cross from Forest Green's Joseph Mills went out for a goal kick after Dominic Bernard could not bring it under control.
A foul on Ogbu gave Town a free kick but the Mariners were unable to make it count, before a free kick at the other end on 20 minutes saw Ebou Adams head over the bar.
Another home attack led to Carl Winchester crossing but his ball was too high for Matt Stevens and Town got it clear.
The visitors won a corner on 26 minutes but the whistle blew for a foul by Davis as Hessenthaler's delivery came across.
Another corner was given after Green went down under a challenge in the Forest Green penalty area but Hanson's header from it was blocked, as was another by Green after Hessenthaler's return delivery.
Winchester was shown the game's first yellow card for a foul on Ogbu 25 yards out and left of centre. Hessenthaler's ball was met by Waterfall but it was cleared after being spilled by home keeper Jojo Wollacott.
A header from Hanson was caught by Wollacott on 35 minutes, before a cross from Ogbu came off Green and went out for a goal kick at the far post.
Two added minutes were played at the end of a first half of few chances for either side, with the hosts' first clear opportunity falling to Bernard in the closing seconds. He played a one-two with Stevens but fired off-target.
That meant the scores remained level at the break, with both teams looking to push on and win the game in the second half.
Dayle Grubb replaced Stevens for Forest Green before the restart and a home corner two minutes in led to a shot from Joseph Mills that flew just wide of McKeown's goal.
After the hosts had the better of the early stages, Town created a chance for Waterfall as Hanson headed the ball down but the defender's weak shot drifted wide.
McKeown gathered the ball at the second attempt after Bernard shot following a Forest Green attack down the left.
At the other end, Whitehouse won a corner on 62 minutes when his left-footed strike was blocked. Hessenthaler's delivery was met by Waterfall and after the ball was not cleared, Town got it back into the box but Hanson's shot went through to keeper Wollacott.
Another chance came when a Hessenthaler free kick was headed away and after the ball came back into the box, it was flicked on by Davis but Hanson, stretching, could only send it wide of the mark.
McKeown went down with an injury on 67 minutes but was passed fit to continue after receiving treatment.
Mondal replaced Kevin Dawson for the home side soon afterwards, before Cook was sent on in place of Ogbu in Town's first change.
And when the dealock was broken by Forest Green on 76 minutes, it was the substitute who made the difference. A cross was cleared as far as MONDAL and he drilled a low shot past McKeown.
A home corrner on 77 minutes was cleared by Waterfall, before Vernam came on for Green and Ring replaced Clifton as Town completed their substitutions.
Hanson headed just wide after a cross from Vernam on the right as the Mariners looked for an equaliser with the clock ticking down.
Davis was forced to head behind and concede a corner at the other end in the last minute of the 90 but it caused no problems as the home side played the ball short an it was put out for a Town throw-in.
Four added minutes were played at the end of the game but Grimsby were unable to force an equaliser and instead, were forced to taste defeat.
They are next in action on Tuesday, when Colchester United visit Blundell Park.
Forest Green Rovers: Jojo Wollacott, Udoka Godwin-Malife, Joseph Mills (C), Matt Mills, Nathan McGinley, Carl Winchester, Dominic Bernard, Kevin Dawson, Ebou Adams, Matt Stevens, Shawn McCoulsky.
Subs: Lewis Thomas, Liam Kitching, Dayle Grubb, James Morton, Taylor Allen, Aaron Collins, Junior Mondal.
Town: McKeown (C), Hendrie, Waterfall, Davis, Hewitt, Clifton, Hessenthaler, Whitehouse, Ogbu, Hanson, Green.
Subs: Russell, Gibson, Cook, Wright, Vernam, Ring, Pollock.
Referee: Leigh Doughty
Attendance: 2152 (283)
Next Up: Colchester Utd (H)