The pacy Partick left-back vividly recalls travelling to Barrowfield to take on Celtic's Under-15 side during a stint at Albion Boys Club in Aberdeenshire, during a year of transition between failing to make the grade at Aberdeen as a kid and returning to senior football with Montrose.
The athletic 6ft 2in player has grown in stature - both physically and metaphorically - since moving to Partick in July 2011, and assuming Forrest can shake off an ankle problem, cannot wait to tackle the same assignment in the first Glasgow derby between these sides since February 2004.
"I'll be directly up against James," said Taylor-Sinclair. "He's a great player for his age and already a Scotland international so it will be a good test for me. Up until now I haven't really had to deal with anyone who has the kind of pace he has so it's going to be challenging. It will be my biggest test so far but then this will be the biggest game of their careers for a lot of our players.
"I've played against him once, although he probably won't remember it. We played Celtic's Under-15s and he was their star man. They beat us 4-1 but I think that I did as well as I could against him. I was quite small then but I always wanted to play full-time football. It was hard when I saw friends like Ryan Jack - whom I went on holiday with this summer - get there before me but I'm here now."
Stopping his fellow 22-year-old, however, is easier said than done. Forrest has come up with big goals in back-to-back matches against Hibs and Ajax, and suddenly appears a key part of the Parkhead side's armoury.
"You can always double up against really quick players," said Taylor-Sinclair. "I think I've struck up a good partnership with Stuart Bannigan and he makes me look better by tracking back and covering for me. But I'm pretty fast as well so I'm looking forward to seeing how I do against James. We might not have as much of the ball as we usually do but I'm hoping I can make him go backwards as well."
In 2004 at Firhill, the Partick side that day included such former Celtic luminaries as Jorge Cadete and Stephane Bonnes, the result ending 4-1 to the visitors. But Thistle will be intent upon proving a point to their supporters.
"It will be a good showcase for our players and gives us the chance to show what we can do in this league," said Taylor-Sinclair, who was linked last season with moves to Cardiff City and Southampton. "This game - and the one against Aberdeen, because I'm from there - were the ones I looked out for when the fixture list was published. Unfortunately for me, when we lost 3-0 at home to the Dons, it was the only game this season when I felt we'd let ourselves down. So this one is massive.
"I think I've been OK this season but I've been saying to the other guys that it's time I stepped up and started getting some goals as well because I get into good positions and I've had a few assists. Attacking has always been part of my game and Jackie McNamara liked his full-backs to get forward, which helped me.
"But I'm also conscious of the fact that, as a left-back, my main job is to defend. We haven't won at Firhill yet this season but hopefully we can beat Celtic and that will kick-start our home form."