Rovers are without a natural left-sided defender after boss Gary McSheffrey released Branden Horton and Cameron John following last season’s relegation to League Two.
McSheffrey wants to add ‘three or four bits of quality’ to his 21-man squad this summer and will cast his eye over some prospective new signings from next week.
He said: “There will be a couple of trialists, a couple of youngsters we’ll have a look at.
"Probably a left-back trialist, it’s an area we need to fill.
“We’ll just see how pre-season goes, if we feel there’s areas we need to fill and players become available we can have a look at them.”
Forward players are also on the club’s radar as they look to address a lack of goals after averaging fewer than one per game last term.
On the decision to release John, who missed eight months of last season with a back injury, McSheffrey said: “Cameron, for me, is a left centre-back. He missed a whole season of football and made seven appearances.
"It was important to get him back out there at the end of the season and show everyone he’s back fit, but we treated that one in terms of how we would try and treat a new player coming in.
"If I brought a new player in and they’d not kicked a ball since last September you (the media) would probably hammer me and the fans would probably hammer me.
"We had to look at some of our retains in that way. As harsh as it sounds, that was really the decision behind it.”
”Good lad, I had him in the youth team, and sometimes you just need that challenge in life and that change.
"You can get a little bit too comfortable at a club where it’s easy for you to turn up every day and train. At times you can drop your levels and your standards.
"This challenge and change of scenery will really, I hope, get the best out of him and I hope he has a really good career.”