Forrester joined Rangers on loan from Doncaster Rovers earlier in the January transfer window. The 25-year-old attacking midfielder will remain at the Gers until the end of the season.
Shiels worked with Forrester at Kilmarnock, and although he admires the former Aston Villa prospect, he has highlighted a flaw in his game.
“Harry’s a dynamic player with good energy,” the 59-year-old told The Daily Record. “Those are his strengths – he likes to run at people. He doesn’t always see the bigger picture though.
“But I’m not running him down – he does have certain qualities and should be an asset for Rangers. I’m just not sure he’s the kind of player they need most right now.”
Forrester has worked with current Rangers manager Mark Warburton at Watford and Brentford, and that should help him at Ibrox in the coming weeks.
The attacking midfielder is a good player and has scored one goal in nine appearances so far this season. The former Watford and Villa prospect will be looking to establish himself in the Rangers first team in the coming weeks.
Rangers are at the top of the Scottish Championship table at the moment with 47 points from 19 matches. Warburton’s side are three points clear of second-placed Falkirk and also have a game in hand.