The keeper was handed a start ahead of fellow shot-stopper and coach Paul Gallacher for Wednesday night's Premiership opener against Ross County.
He didn't let Jags boss Alan Archibald down as he kept a clean sheet and helped Thistle to a superb 4-0 triumph to get their campaign off to a perfect start.
Injury cost Fox his place in the side last term as Gallacher played a key role in the Jags' retaining their top-flight berth.
And the keeper knows he will have to remain at the top of his game to stay between the sticks in the coming weeks.
Fox said: "To be honest I didn't really expect anything until Friday when the team was named. I knew Paul could have played or I could have played, it was that close, and I was just happy to get the nod.
"There was a wee bit of pressure to perform, but I enjoyed the game and it was a great start to the season.
"Of course, competition drives you on and I think you saw that at the start of last season with the way I started as well.
"Gall was there pushing me all the way and I think that kind of showed in my form.
"I ended up getting a Scotland call-up from it.
"When my form did dip and I got injured, Gall came in and produced, so it's competition and it will drive you on - you can't rest on your laurels."
With their first win on the board, Thistle head to Dundee this afternoon aiming to make it two from two in the top flight.
In a season of missed opportunities and costly mistakes, it took Archibald's side until February to take all three points at Firhill last term and they eventually finished tenth in the table.
And Fox hopes the early home triumph can be a springboard to success for the Jags as they set their sights on attaining a loftier league placing this season.
He said: "There was a lot of pressure on us last season, especially with us not getting that home win for so long.
"But that's been lifted right from the start this season with us getting a home win so soon.
"I think there will be an expectation now more than anything and as a group we need to go out and get the results we need to push as high up the table as we can.
"There wasn't a lot of expectation on us last season and we started fairly well with a couple of draws and a couple of wins early on but that was away from home.
"So if we can produce the away form we showed last season coupled with the home form we've started with this time, I don't see why we can't do well."