Ex-Spennymoor United and Bradford Park Avenue ace Adam Boyes smashed in four goals as NPL East title-chasers Marske romped to victory, ex-Whitby Town ace Matty Tymon also scored twice and James Fairley the other.
Agnew said: “They were far superior to us, we started out and had a bit of a go at them but they got goals early on and when we tried to switch this to sitting in they still managed to get more goals.
“It could have been even more than seven, they had some very good players who have played at a higher level.
“I have never been beaten by that margin as a player or as a manager.
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“It is hard for me to process that we are going to be battling at the bottom end of the league table.
“Maybe I need to look at trying to change my tactics a bit now with us battling near the bottom, possibly keeping things tight and grafting for the odd point here and there may be wiser.”
Agnew is hoping Leon Dawson will return for the Seasiders when they travel to promotion-chasing Worksop Town on Saturday but he was hit by more injury worries heading into the weekend.
He added: “Danny Earl has been suffering with Plantar fasciitis, a painful heel injury, but it is something that can be managed and I am hoping he will be okay for Saturday.
“Lewis Dennison also picked up a groin injury so we will need to check on him at training too.
“Declan Parker is not available at the weekend, and with us having so many other players out and only fielding two subs I’m actively looking to sign a couple more players in time for the Worksop match.”
Town’s most recent recruit, forward Flynn McNaughton, made his debut on Saturday after only completing his move from Selby Town the day before.
Agnew said: “Flynn was given a proper baptism of fire to make his debut in that game!
“I was very happy with how hard he worked, especially as he was playing out of position out wide.
“I have been watching Flynn for some time now and it is great to get him, he has good qualities and is a good finisher.
“I am in talks to get a couple more new lads in at the moment.”
Agnew is hopeful that the injury problems may ease a touch this week, as Will Annan and Jack Bulless may be back in training on Thursday evening.
The manager added: “Matty Dixon is still out for a couple of weeks, Joe Lamplough is likely to be out for a long time and I am not sure when Pete Davidson can return.
“I cannot fault the group of lads who have had to play pretty much 90 minutes every game for the past few weeks, especially as a lot of them have been forced to play out of position, they are giving everything at the moment.”