Jayson Castro nailed the go-ahead basket as TNT Tropang Giga completed an 86-84 escape of San Miguel Beer in Game 1 of the Philippine Basketball Association Philippine Cup best-of-seven final series Sunday night at the Araneta Coliseum.

With only 1.6 seconds remaining, Castro again shone and drained the game-winning pull-up jumper to give the Tropang Giga a 1-0 headstart in the race-to-four duel for the All-Filipino crown.

Castro finished with 15 points and three rebounds, but it was Roger Pogoy who led the attack with 26 points on 10-of-17 shooting, to go with three rebounds and two assists.

Mikey Williams scored 15 of his 21 markers in the second half to go with four boards and one steal.

It was a thrilling finals opener that delighted thousands of fans in attendance, including the visiting Gilas Pilipinas star and Utah Jazz stalwart Jordan Clarkson.

Clarkson is in town to serve as a naturalized player for Gilas in the fourth window of the FIBA World Cup Asian Qualifiers against Lebanon on 25 August and Saudi Arabia on 29 August.

"In the end, it was great that Jayson made the shot. But the better thing is we gave ourselves a chance," TNT tactician Chot Reyes said.

"We really clicked at the right time, San Miguel was outplaying us. This is the finals, the only way we can beat a team like that is for all of them to contribute."

San Miguel big man June Mar Fajardo went off to a rousing start with a perfect 14 points on 7-of-7 shooting to grab a 49-37 lead at the half.

But it was Pogoy who willed the Tropang Giga back, spearheading a 10-0 attack before Poy Erram's three-point play gave TNT its first taste of the lead halfway the third.

A steal from Pogoy gave the TNT its biggest lead at 10, 79-69, but Fajardo worked his way to trim the deficit and Vic Manuel tied the game at 84-all with only 54 seconds remaining in the payoff period.

But Castro spelled doom for the Beermen after receiving the inbound pass from Ryan Reyes and hitting the jumper over the outstretched arm of Simon Enciso.