The 7-0 demolition of Airdrie United took Jackie McNamara's side back to the summit of Scotland's second tier, with O'Donnell turning in a man-of-the-match performance.
With seven wins from their opening nine league fixtures, Thistle are the ones to catch, but have title rivals Dunfermline and Morton breathing heavily down their necks.
Next up for the Jags is a trip to Falkirk this weekend before they kick off their Scottish Cup campaign against Cove Rangers.
With a crunch clash at home to Dunfermline to come early next month and the visit of Morton to look forward to on Boxing Day, the coming weeks could prove crucial in the title race.
He said: "It is safe to say that we would have taken that (start) at the beginning of the season.
"It is, however, just the first quarter, and we need to keep building on it and hopefully, come Christmas time, we will really be pushing hard at the top of the league.
"There's a lot of football to be played, especially during the Christmas period when you start to pick up injuries and illness, and the squad starts to get tested. We have the belief we do have a squad which is strong enough.
"You look at a player like David Rowson. I'm not sure how many years he's been at the club, but he is sitting in the stand and can't get a place on the bench, so you know how strong the competition is for places.
"He's certainly been a great player for the club and, while he might not be quite fully recovered from his injury, he's still struggling to get into the squad and I think that shows just how strong we are at the moment."
Thistle have hit the goal trail as they have put down an early title marker and booked a place in their first cup final in 41 years, with the Ramsdens Cup clash against Queen of the South coming up next spring.
Despite captain Alan Archibald missing the Jags' last two fixtures, their youthful defensive line have proved more than up to the task and O'Donnell is delighted the rearguard are playing their part in Thistle's success.
He said: "That's the second game in a row we've kept a clean sheet and shows that us young boys are doing ourselves justice. Managers say that if a player is good enough then he is old enough.
"Conrad Balatoni is certainly good enough, and has shown that in the last couple of games, and so, too, is Aaron Muirhead, who at the moment is the old head of the back four.
"We're fortunate, too, that we have Scott Fox playing behind us."