Paul Simpson wasn’t surprised by Grimsby's amazing FA Cup exploits – and has warned Carlisle United that they’ll be facing an in-form side this weekend.

The Mariners return to league action at Brunton Park tomorrow, three days after knocking Premier League side Southampton out of the cup.

While Grimsby are 16th in League Two, Simpson said they have been showing good signs recently – capped by their history-making efforts at St Mary’s.

“I thought they were excellent. I've got to say I wasn't surprised, because I'd already watched their games against Leyton Orient and Northampton before the Wednesday night game, so I knew there were a good side,” said Simpson.

“I knew they were able to cause problems and I've got to say I thought they were an absolute credit to the EFL, and I don't think Southampton can have any grumbles that Grimsby certainly deserved to win the game.

“We know this is going to be a tough game against the side who have earned the right to be in the later stages of the FA Cup.”

Third-placed Carlisle are hoping to strengthen their automatic promotion claims against a Mariners side who are better on the road than at home so far.

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Grimsby have claimed seven of their ten league victories on their travels – but Simpson says Paul Hurst’s side must be respected wherever they play.

“I think they’re a threat at the moment because they've got a really good mix of experience and youthful players,” he said.

“They brought Danny Lloyd in from Cheltenham on loan in January and he's causing all sorts of problems, Harry Clifton’s getting goals, John McAtee causes problems, and they've just sort of come across a shape that's working for them over the last few weeks.

News and Star: Two Gavan Holohan penalties sealed Grimsby's memorable cup win at St Mary'sTwo Gavan Holohan penalties sealed Grimsby's memorable cup win at St Mary's (Image: PA)

“They find themselves four games unbeaten now. I don't think there's any real difference between home and away because the truth is, last weekend, if they hadn't missed the penalty, they'd have probably beaten Orient.

“Let's not kid ourselves and think that this is going to be easy. They're going to come in full of confidence after what happened on Wednesday, and we don't know what the sort of emotional state they're going to be in after what went on.

“We've just got to make sure that we're right and that if there is any little sort of chink in their armour, we make sure that we go and exploit it.”

Simpson admits it is not easy to guess how Grimsby will perform so soon after their huge cup night.

“We have no idea. That’s the fortunate thing about us focusing on what we can do,” he added.

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“What we’ve got to do is make sure that we start properly and if they have got any sort of hangover from Wednesday night – whether that be an alcohol hangover or just a pure joy hangover from what went on – we've got to make the most of it.

“If we focus on ourselves and show why we are third in the table after 33 games I'm quite sure we'll give ourselves a good chance of getting the result.” 

On opposite number Hurst, meanwhile, Simpson said: “I’ve come across him a few times on the management side.

“I like him. I think he's a really sensible bloke and he organises his teams well.

“He's got a real good manner about him and I'm looking forward to them coming, and I'll certainly congratulate them and wish them well for the next round.

“But I don't want them to go away from here with anything at all on Saturday afternoon.”