Cathcart has been recovering from long-term injury and is determined to hit the ground running next season.
He told manutd.com: "Since the U18s I've been on loan at Antwerp for six months, but I was a bit unlucky with injuries. The next season I was at Plymouth.
"I played a lot of games there and I thought I did quite well. I came back to United and had a few games in pre-season, then went out on loan again to Watford, then picked up an injury and I've been out since Christmas. So I'm just coming back to fitness now.
"Yeah, I've been in nearly all summer. I've had some time off, but otherwise I've been working hard. I've never been injured over the summer so I'm used to having six weeks off. It's different! But I'll be a lot better and a lot fitter for it."