The 21-year-old spent 2020-21 on loan at Hull City where he won the League One title.
With the Blades dropping into the Championship next season, interim manager Heckingbottom thinks the youngster will have to come into consideration for a place in the first-team squad.
Slater, who previously had loans at Carlisle United and Scunthorpe United, grew into the team as the season went on, making eight of his 11 league in the final nine matches deputising for injured captain Richie Smallwood.
“He’s done fantastically well,” said Heckingbottom, who was the Blades’ Under-23 coach before temporarily stepping up to the senior role in March. “He’s gone out and earned his gametime. As the season went on he got more and more gametime which speaks to him and how he’s performed in a team that was top of the league.
“It’s a great reflection on him. We’ve had him watched this season and his position for me is simple in what he’s saying to the club and the new manager – he needs to have a look at him.
“We as a football club have to make a decision. If he’s not quite ready we have to keep him moving in the right direction but, hopefully, he’ll have done enough to get in the squad and if he comes back in even better shape he might even get in the team, that’s what we’re hoping for with our young players.
“When he comes back into the building we’ll want him to attack pre-season in the same way to make the right impression.”
Slater has made three first-team appearances for the Blades, scoring on his 2016 debut in a Football League Trophy win at Grimsby Town, and making substitute appearances at Preston North End and Ipswich Town in the 2017-18 Championship and FA Cup respectively.
Blades midfielder John Lundstram’s contract expires this summer and Norwegian international Sander Berge looks certain to lead the list of sales, with Arsenal at the head of a list of clubs reportedly monitoring the former Champions League player.
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