The Partick Thistle defender missed the opening stages of last season due to injury and didn't play a competitive fixture until November.
He got more vital minutes under his belt as Alan Archibald's side drew 1-1 with Dumbarton on Saturday and is set to be involved once again on Sunday when the Jags head to Belfast to face Glentoran.
The start of the campaign is just a couple of weeks away now and the former Rangers and Dunfermline stopper can't wait to get down to business when Thistle host Ross County on August 13.
McMillan said: "The most important thing in pre-season is getting minutes under your belt and I got another 45 on Saturday and a few of the boys got a bit more than that.
"Everything is going well and we are all looking fit.
"It took me too long to get going last year but I have forgotten about that, I am looking forward.
"I am feeling good, I have done everything I had to do so far in pre-season.
"I have not had any niggles or anything like that. I am feeling good, as is the rest of the squad.
"We are looking well in the games and in the tests and we just can't wait to get going now."
After finally winning his fitness battle last season, McMillan became an integral part of Archibald's plans as Thistle retained their top-flight status for another term.
He will compete with Stephen O'Donnell for the Firhill right-back berth in the coming weeks as he looks to retain the jersey he ended the campaign with.
And the 25-year-old insists he can take nothing for granted as Archibald considers his options and looks to bolster his ranks ahead of the new season.
He said: "It is a fresh start for everyone. It is healthy to have competition for places right across the team and we have that with myself and Stephen O'Donnell at right-back.
"The gaffer is looking to bring in a couple of players as well so it will be interesting to see the team at the start of the season.
"Hopefully I have got that starting jersey. But it is going to be a long season, there are always changes and injuries and suspensions so we will need everyone."
While Archibald has two quality right-backs on his books, he remains in the market for rearguard reinforcements as he looks to fill the void left by Aaron Taylor-Sinclair's switch to Wigan and recruit another centre-back.
The Jags boss cast his eye over four defensive trialists in the weekend draw against the Sons and McMillan is happy to play his part and use his versatility to ease Archibald's worries.
He said: "They are two of the positions that he has identified. It is well documented that we need a centre-half and a left-back with Sinky going.
"That is up to the manager and they will be doing their work behind the scenes.
"We are just getting on with it and doing everything we can to fill the gaps just now.
"I have played left-back and I have played centre-half and there are a couple of other boys that could do the same.
"We have got good strength in depth but I am sure there will be more coming in."