Celtic do not need "a major overhaul", says Brendan Rodgers, but the manager expects to see the Scottish champions "doing more" in the transfer market.
Rodgers has recruited goalkeeper Ross Doohan, forwards Benjamin Nygren and Callum Osmand, plus defender Kieran Tierney, while left-back Greg Taylor has joined PAOK.
"We're not needing a major overhaul of the squad, but freshness is so important," Rodgers told club media.
"Some of these guys have been here a long time. It's so important, even in a winning squad, that you refresh that and reset the competition in the squad. We've done some really good business up until now."
However, he stressed: "I see us doing more to get us set up for hopefully what will be a really exciting season."
Tierney departed Celtic for Arsenal in a £25m transfer six years ago and the Scotland international has returned Glasgow as a free agent.
"Sometimes top players like that might come back later on in their career, but we're getting Kieran at 27 years of age," Rodgers said.
"I was with him during the summer, so I know first hand as well how excited he is to be here and I'm looking forward to seeing this new version of Kieran, having had the experience in the Premier League and playing at a top club like Arsenal.
"He'll come back here with greater maturity both as a person, as a professional and tactically and now we can really get the benefits of that."
Of Sweden cap Nygren, Rodgers added: "He's a leader on the pitch and he produces on the pitch in terms of his goals he scores, what he creates and he's got real good physicality.
"I'm really looking forward to seeing him adapt to how we play."
