The Sheffield-born midfielder made his Tykes debut as a 16-year-old at Derby in September 2011 and made three further appearances in the Championship under former boss Keith Hill before struggling with a long-term hip problem that halted his meteoric progress.
But Digby, now 18, is training with the first-team squad again in Spain and is hoping a strict fitness regime will help keep him injury-free as he bids to become a key player for manager David Flitcroft.
"It's been a frustrating time but I've come back in and fitted in well," Digby told the club's official website.
"It doesn't seem like I've been away which is good and the boys have been brilliant with me.
"I'm doing everything I can to prevent the injury coming back.
"I've got so many different exercises to do. I have an hour's work before training. I'll crack on now.
"We're all here to challenge for a place and I'm really looking forward to the new season."