Grimsby Town opened their season with a heavy defeat as Forest Green Rovers won convincingly at Blundell Park.
On a sunny afternoon and with a big home crowd watching, the Mariners were ahead at half-time after Mitch Rose converted a penalty on the half-hour.
But the visitors hit back through Carl Winchester six minutes after the break and a bizarre own goal by Danny Collins gave them the lead, before Christian Doidge added a third.
And their victory was completed when Doidge was gifted a second goal six minutes from time.
Town boss Michael Jolley's first starting XI of the new campaign saw James McKeown start in goal behind a back three of Harry Davis, Alex Whitmore and Collins.
Harry Clifton and Paul Dixon took up wing-back poitions on the right and left respectively, with Rose, John Welsh and Martyn Woolford forming a central midfield trio as JJ Hooper and Jordan Cook began in attack.
The Grimsby substitutes were Reece Hall-Johnson, Jake Hessenthaler, Louis Robles, Andrew Fox, Akin Famewo, Charles Vernam and Sam Russell.
Forest Green included former Mariner Gavin Gunning in their starting line-up, while strikers Reuben Reid and Doidge would be out to get the goals for Mark Cooper's men.
Town kicked off attacking the Pontoon Stand end and the home side's first two attacks came through the long throw of Rose, although neither managed to cause significant danger.
A foul on Cook gave the hosts a free kick in a dangerous position on 11 minutes but Welsh sent his shot over the bar.
At the other end, Reid did well to control a cross-field pass from Liam Shephard and send the ball across the penalty area but it was too far ahead of Doidge.
A foul by Collins gave the visitors a free kick on the right but after the ball was sent into the box, Reid was penalised for a handball.
Another long throw, this time from Dixon, was headed over his own keeper by Gunning but the ball ran across the six-yard line and was picked up by Rose, who was fouled by Joseph Mills.
The defender was booked before Dixon's resulting free kick was put behind for a corner, which was eventually dealt with after Collins' header was blocked.
A weak, 30-yard shot by Doidge went straight through to McKeown, before a low cross from Shephard was cleared by Welsh.
Good hold-up play by Reid then set up a chance for Forest Green on 23 minutes, although Winchester's shot from 20 yards flew off-target.
The visitors were starting to look the more threatening in attack and they caused more problems down the left on 25 minutes as Mills's cross was retrieved by Shephard. He chipped it back towards the far post, where Mills' header was blocked and an offside flag eventually came to Grimsby's rescue.
Shephard then fired over the bar from a narrow angle as Forest Green continued to create the better chances.
But when the first goal came on the half-hour, it was the Mariners who took the lead against the run of play. A chipped cross from the overlapping Woolford led to a handball by Lloyd James inside the box and referee Martin Coy pointed to the penalty spot. ROSE stepped up and beat the dive of keeper Robert Sanchez to find the bottom corner of the net.
Reece Brown shot wide from 18 yards after a good build-up as the away side looked for an equaliser.
A run from James down the left on 40 minutes took him into the Town box but his chipped cross to the far post dropped out of play for a goal kick.
Dixon was booked for a foul on Shephard on the right and after James sent the ball into the box, Farrend Rawson's header dropped wide.
One aditional minute was played at the end of the half and a Grimsby attack ended with a 20-yard shot from Welsh being caught by Sanchez.
That proved to be the last chance of the half, meaning Town kept their one-goal advantage at the break.
No changes were made before the restart an the first chance of the second half fell for Rose after he was found by Woolford on the edge of the box. The midfielder's shot was deflected away for a corner, which was headed behind by Gunning for another one. This time, the visitors cleared.
Six minutes in though, the away side were back on level terms when a cross from James was headed down and WINCHESTER took a touch before finishing from close range.
A foul by Rose gave Forest Green a free kick in a dangerous central position as they looked to complete the turnaround but Brown's shot from it was poor and Town were able to clear.
At the other end, Woolford's pass to Dixon opened up space for the left wing-back and he went on to find Hooper, who turned the ball just wide of the near post.
A double substitution for the Mariners just after the hour saw Hessenthaler replace Woolford and Hall-Johnson come on for Dixon, while Theo Archibald was sent on in place of midfielder George Williams for the away side at the same time.
Forest Green took the lead in bizarre circumstances on 67 minutes as a throw-in went to Collins and he turned to pass the ball back to McKeown but the keeper was not on his line and it rolled into the empty net for an own goal.
And it got worse for the Mariners three minutes later as Forest Green made it 3-1. A corner from the left was met by DOIDGE, who headed the ball past McKeown and into the net.
Vernam replaced Davis in Grimsby's third and final substitution as the manager looked to an extra attacker in a bid to force a way back into the game.
Hooper sent a shot over the bar from the edge of the box on 83 minutes as Town attacked in search of a goal that would halve the deficit.
But instead, the away side were gifted a fourth goal when a weak back-pass from Hall-Johnson was capitalised on by DOIDGE, who rounded McKeown and tapped into the empty net for 4-1.
Hessenthaler worked his way into the box and won a corner but Town were unable to profit from it, before a lengthy stoppage came when keeper Sanchez went down and had to be treated.
Six minutes of added time was signalled by the fourth official and those added minutes were seen out by the visitors, leaving the Mariners to reflect on a bad opening day of the League Two season.
They will now look to regroup and secure a more positive result when they travel to Macclesfield Town on Saturday.
1 James McKeown
24 Harry Davis
25 Alex Whitmore
6 Danny Collins
2 Paul Dixon
15 Harry Clifton
4 John Welsh (C)
16 Martyn Woolford
8 Mitch Rose
11 Jordan Cook
9 JJ Hooper
23 Sam Russell
12 Akin Famewo
19 Andrew Fox
2 Reece Hall-Johnson
7 Jake Hessenthaler
14 Louis Robles
18 Charles Vernam
Forest Green Rovers
1 Robert Sanchez
2 Liam Shephard
23 Joseph Mills
6 Farrend Rawson
16 Gavin Gunning (C)
4 Lloyd James
10 Reece Brown
7 Carl Winchester
9 Christian Doidge
26 Reuben Reid
11 George C Williams
13 James Montgomery
5 Lee Collins
32 Haydn Hollis
18 Theo Archibald
20 Paul Digby
8 Dayle Grubb
14 Tahvon Campbell
Referee: Martin Coy
Attendance: 5,879 (72)