The Firhill youngster replaced Jordan McMillan at left-back early in the match as Alan Archibald's side continued their unbeaten start to the campaign in an eventful 1-1 draw with Dundee.
Keenan featured regularly in pre-season for the Jags but with no new left-back arrival so far this summer, Archibald decided to go with experienced stopper McMillan for the games with Ross County and the Dees.
The door is now open after an impressive showing at Dens Park and Keenan is eager to grab his chance as attentions turn to Saturday's clash with Hamilton Accies.
"It was a great experience," he told ptfc.co.uk "We were unlucky with the result but we held on with 10 men.
"It's harder to get up and down the wing with 10 men. I've always tried and I've learned a lot from the other defenders who are at the club.
"When we had 10 men Dan Seabourne and big Conrad (Balatoni) spoke to me all the way through and that really helped me along.
"I thought I might have been in with a chance of starting after pre-season but the gaffer went with Jordan, with him getting injured hopefully I'll be slotted in next week against Hamilton and continue from there.
"It's great to eventually get off the bench. It's a good thing for me and what I've been waiting to do after pre-season and the gaffer gave me the chance. Hopefully I can build on this."
"I'm always learning and trying to build on what other players have done and take it into my game.
"I hope I can kick on from [Saturday], starting with next week's game against Hamilton."