McGuire won seven Super League titles for his hometown club, four of them under McDermott including last season’s glory which came just before the star half-back moved to Hull KR.
But McDermott - who had been in charge since 2010 and is the competition’s most successful coach - was sacked on Monday with struggling Leeds hanging onto a top-eight spot.
They have not won a Super League game since April when, ironically, they defeated McGuire's current club Rovers at Craven Park.
Asked about his former boss being axed, he told The Yorkshire Post: “I'm probably not surprised, if I’m honest.
“Leeds have lost seven on the bounce and that’s pretty tough to take for a club of their stature.
“The timing is probably a bit of an issue now. Is someone going to be ready to jump in?
“I think it’s pretty crucial that there is someone in charge in this period of time.
“What Mac’s achieved at Leeds has been phenomenal really but I believe there is always a time when the coach’s time is up.
“When you get the same sort of style and same messages every week I think it can become a little bit stale.
“A freshen up for the lads and everyone at the club will be good for the team.”
McGuire does not feel Rhinos chief executive Gary Hetherington necessarily made the decision now in fear of the club eventually being relegated.
“I think Gary is probably looking more for a reaction from the players,” he said.
“I actually think it's not great timing but again when is it good timing to get rid of your manager?
“I think he’ll be looking for the players to come together and, in my time there, it was very player-led.
“You had to look after yourself and work together as a team.
“Especially in tough situations we always dug ourselves out of it and I'm sure the lads there will do the same.
“It’s sport isn’t it? If results aren’t what the club needs or the club and fans demand then changes have to be made.
“But Mac's still got a lot to give the game.
“Although he might take a bit of time out now I think he’ll definitely get back involved again as he's too good a coach not to.”