Rashford's route back to regular involvement looked improbable not long ago, having fallen out with previous manager Rúben Amorim before spells away on loan at Aston Villa and Barcelona - the Catalan club opting against triggering the £26m option that would have made his move permanent.
With Tuesday's deadline now bearing down, he looks set to stay at Old Trafford for the rest of the season regardless.
Maguire was full of praise for the impact Rashford made against Ipswich.
"He's a great talent. He's always a threat," the defender said. "If Marcus wants to be here, wants to work, wants to improve and help the team, of course we're willing to have him in the team.
"He could still do a lot more and I think he'll say he can do more but if we keep him fit, we keep him happy, he keeps driven and hungry, he's a great asset to have."
Rashford's application and enjoyment of the game have both been questioned at points since Erik ten Hag's time in charge, though his loan spells under Unai Emery and Hansi Flick are thought to have done him good, with manager Michael Carrick's existing relationship with the forward seen as a further advantage.
Maguire, who went through his own difficult spell losing both his place and the captaincy under ten Hag, offered context for the criticism Rashford has faced.
"You've got to remember Marcus has had a wonderful career for this club. But when you play at this club for numerous years, there's going to be bad seasons, and when the bad seasons come everyone piles on you. That's part and parcel of playing for this club," he said.
"As a club, we haven't been perfect from top to bottom. We haven't been challenging at the top end. So, Marcus has been part of a rough ride for Manchester United. When that happens, players get dug out. I've been through it. He's come back in, really fit and sharp and we're excited to have him."
Kobbie Mainoo, another player Carrick has worked to rebuild after being overlooked by Amorim and then left out of England's World Cup squad by Thomas Tuchel, also impressed on his first start of the season. Maguire was effusive about the midfielder's display.
"I thought he was brilliant. To say he hasn't had many minutes in pre-season, he was magnificent," he said. "His work without the ball has improved so much since Michael's been in. He's becoming a real monster in there, wins a lot of second balls and a lot of duels.
"The thing is he's so young. If we want him to play for this club for another 10 years, there's going to be times where he's going to go through a patch like I spoke about with Rashy and myself. But that's part and parcel. He's really level-headed, really composed and has great belief in his ability. He's going to be a magnificent player for this club for many years."