Michael Jolley lambasted his Grimsby side after a meek 2-1 defeat handed Stevenage their first Sky Bet League Two win of the season.
Kurtis Guthrie and Charlie Carter struck before the break as Stevenage came out firing in their bid for a league win at the 13th attempt.
Ahkeem Rose’s late strike ensured a nervous finish but the Grimsby equaliser was not forthcoming, leaving Jolley fuming come the final whistle.
“I think the comeback was almost irrelevant, the first 45 minutes were our worst performance of the season by a distance. I could have made 11 subs at half-time,” he fumed.
“I’m really disappointed with the way we went about the game in the first half. We gave two incredibly bad goals away, didn’t create enough chances, and we didn’t move the ball well enough.
“We improved somewhat in the second half, I thought some of the players who came on [Moses Ogbu, Ahkeem Rose and Charles Vernam] did well, but we gave ourselves too much to do.
“We can’t start any game in the manner that we did against any opponent.
“It’s not acceptable, it’s not good enough and we’re very upset about it.
“We’ve had a good discussion in there, the players are very clear on where I stand with regard to the first half and let’s hope that we can see an improvement.”
Luther James-Wildin found Guthrie in the area with a driven cross, with his clever flick beating visiting stopper James McKeown at the far post for the opener.
The home side doubled their lead shortly before the break when Carter swept home after 43 minutes.
Grimsby eventually pulled one back when substitute Rose blasted home from a counter-attack on 79 minutes but the hosts held on, much to the relief of Mark Sampson.
“I’m really happy for the players, the staff, supporters and the football club. That result has been coming,” he said.
“We knew we’ve been starting games well and showing enough in games to win games, but ultimately we just needed to get over the line in a league match.
“Whatever we feel about this performance, which in parts it was outstanding again, parts we’ve got some big learning to do, it was just about getting over the line.
“The feeling in that changing room is very different to what it was this time last Saturday, I promise you that. There is a feeling and a sense of optimism, and confidence, and belief that we needed this (win) to get the ball rolling.
“That’s one defeat in five, two wins in a row (in all competitions), that’s a team that’s definitely moving in the right direction.
“We’ll keep this snowballing rolling down this hill.”