David Bolland scored the winner midway through the third period as Toronto downed the Senators 3-2, but the focus was on Pageau's play after the Ottawa loss.
Pageau nearly gave the Senators a 3-2 lead on a short-handed breakaway moments before Bolland's goal.
"When you have a good chance like that you don't want to miss it," said Pageau. "The goalie made a good save but hopefully the next one will go in."
Bolland scored on a backhand at 10:25 of the third period to send the Leafs (2-0-1) to victory. Nazem Kadri and Mason Raymond had the other Toronto goals.
"I thought we came out pretty flat and weren't at our best in the first, but we came out and I thought we were pretty good the rest of the way," said Leafs captain Dion Phaneuf. "It wasn't a full line up for both teams and (training camp) is about getting in shape.
"It's an adjustment for the young guys and it's an adjustment for the older guys. It's about timing but I think overall we played well. "
Fredrik Claesson and Andre Petersson replied for the Senators (2-1-0) while Patrick Wiercioch had two assists.
Pageau also made an impact with his physical play. After a hit along the boards, Toronto's Nazem Kadri and Pageau traded punches. Pageau was assessed a double minor, while Kadri wasn't penalized.
"I was a little bit surprised," said Pageau. "It was a clean hit and we both exchanged some punches so I don't know why I got the double minor."
Pageau had two goals and four points in nine regular season games with Ottawa last season, and added another four goals and six points in 10 playoff games.
Earlier this month he was the leading scorer in a rookie tournament featuring the Senators, Maple Leafs, Chicago Blackhawks and Pittsburgh Penguins.
Thursday was Pageau's first pre-season game and he finished with over 14 minutes of ice time and four shots on goal in his bid to convince Ottawa's coaching staff he deserves to stay with the big club.
He's got at support from important corner: newly minted captain Jason Spezza.
"I'm really a fan of Pageau," said Spezza. "I think he creates a lot out there, he has great hockey sense, he competes. He's a little guy but he's always going to the dangerous areas and he's definitely putting his best foot forward."
Jonathan Bernier started in goal for the Leafs but was replaced by Drew MacIntyre who played the final two periods. Both were appearing in their second game of the pre-season.
Craig Anderson made his pre-season debut for the Senators and played the opening two periods for the Senators while Nathan Lawson got into his second game of the pre-season by working the final 20 minutes.
The teams entered the third period tied 2-2 following a second period that saw three goals in the final five minutes of the period, including two by the Leafs 19 seconds apart.
While on their second power play of the game, the Leafs finally got on the scoreboard as Kadri beat Anderson at 15:33.
While that goal was being announced, the Leafs took a 2-1 lead as Raymond found the back of the net behind Anderson.
It looked as though the Leafs would head into the second break with the lead but Wiercioch found Petersson cutting into the middle of the ice and the rookie beat MacIntyre with a back hand from the slot.
Claesson scored the only goal of the first period as his slapper from 10-feet inside the blue line somehow eluded Bernier and went in off the crossbar.