The team that has won the third quarter has captured each game in this series.
The Celtics lead 3-2 in this best-of-seven affair, with the Sixers looking to stave off elimination in Game 6 Wednesday in Philadelphia.
How impressive and unpredictable was Bass' third quarter explosion?
The 18 third-quarter points were just one shy of his all-time playoff career mark, when he totaled 19 for the Dallas Mavericks on April 22, 2008 at New Orleans.
His best total in the previous four playoff games against the Sixers was 15 in Game 4.
"For me, I think it was me taking advantage of my opportunity," Bass said. "They have been doubling Paul [Pierce] and we have a few good players on the team they have to focus on, and that left me open tonight and I was hitting the shots."
The 6-8, 250-pound Bass is a power forward who has a little small forward in him as well.
Bass has a solid perimeter game, but he also has the speed and power to drive to the basket, where he executed several dunks with authority.
"He had too many easy baskets, too many dunks," Sixers coach Doug Collins said of Bass.
In the third quarter Bass hit 6 of 7 from the field and all six free throws. For good measure, Bass added two rebounds and two steals.
Nothing could forecast this happening, especially since Bass had a nondescript five points in the first half.
"I thought he kept the game simple in the second half," Celtics coach Doc Rivers said. "He didn't try to do too much and he let the game come to him and trusted his teammates."
In turn, they kept trusting Bass.
"The difference was his energy," Rivers said. "He went after rebounds, played with force and let himself go."
If Bass was the surprise of the second half, imagine the role that Greg Stiemsma played in the first quarter.
In scenarios that had the Celtics winning Game 5, few subplots had Stiemsma as a leading character, or even seeing meaningful minutes.
A 6-foot-11 rookie from Wisconsin, Stiemsma entered the game for Kevin Garnett with 5 minutes and 46 seconds left in the first quarter.
In that span he promptly hit all four field-goal attempts for eight points while also blocking a shot.
His outburst was more shocking than thaty of Bass.
"Steamer really gave us a lift," Rivers said.
Stiemsma didn't even get off the bench in Game 4, and in the previous three games had a total of two points.
In this game he would finish with 10 points, hitting all five field-goal attempts - just another surprising development in a series that hasn't followed a traditional script.
Contact Marc Narducci at 856-779-3225, email@example.com or follow @sjnard on Twitter.