The Warriors have lost several experienced internationals, including Huw Jones, Adam Hastings, Jack Dempsey, Johnny Matthews, Jamie Bhatti and Sione Vailanu.
Jamie Ritchie, Bayley Kuenzle and Ruwald van der Merwe are the only new arrivals, with the South African back-rower still to join up with the squad.
Forrest Told The Scotsman: "In terms of bringing players in, the way the squad is just now is probably how it's going to look. Obviously that might change if we pick up long-term injuries in certain positions that put us under stress.
"I would say there were probably similar conversations happening last year [around recruitment] when the likes of Seba Cancelliere left, Henco left, and TJ left.
"There were probably similar things said about these guys leaving and not being replaced by a similar quality. And, while we've not won a trophy, statistically we won more matches last season than we've ever done in the past and finished top of the URC regular season.
"So, we're looking at the positives. Yes, we've lost some quality internationals but we're very confident in terms of the younger players that we've got in our group. We feel we've got a lot of them here that are ready to step up now, while we've still got the core group of senior internationals that I think everyone knows what they can do.
"We're still pretty confident that the blend that we've got in the squad, and the competition we've got for places, will put us in a pretty good position this year."
Glasgow topped the URC regular-season table last term and reached the Champions Cup quarter-finals, but their trophy hopes ended with knockout defeats by Toulon and the Bulls.
Forrest believes the foundations remain strong and says the focus during pre-season will be on finding the small improvements required to turn those tight knockout games in Glasgow's favour.
He added: "The first thing is that there's a bit of reinforcement there for everyone. A lot of our big rocks we talk about - that's the language we use in attack and defence, set-piece - are some of the best in the URC, in Europe and in world rugby.
"So the core of what we do, especially attack and defence, we're not going to change. I feel we've got an identity on both sides of the ball. Ultimately, where we fell down was two knockout games, one against Toulon in Europe and then obviously the Bulls.
"There's probably been some similarities with Scotland over the last 12 months and they've had a really positive summer. So, our big rocks aren't going to change. Ultimately, we just need to look at those little one-percenters about what gets us over the line in those knockout pressure matches."