In early 2015, Tristan Thompson was in the middle of his fourth season in the NBA, coming off the bench for the Cleveland Cavaliers after several seasons as a starter.

The Cavs had changed. LeBron James was back, and Kevin Love had been brought in. Thompson, whose focus was rebounds and defence, became the team's strong sixth man. When he turned down a four-year $52-million (U.S.) contract offer, the general reaction was disdainful laughter: Thompson was a fool to think he was worth more.

This was standard. Thompson had been doubted ever since the Cavs chose him No. 4 in the 2011 draft.

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One man knew Thompson's worth: James. When injuries beset the Cavs in last year's playoffs, Thompson – Double T in the parlance of James and friends – played his best basketball. Then, before this season started, Thompson scored a five-year $82-million deal. He came off the bench again in the regular season – but in the playoffs he's started every game, and again played his best basketball.

Against the Golden State Warriors – vying to be remembered as one of history's great teams – Thompson has been fierce on the boards and excelled on defence. In a must-win Game 6 on Thursday night, Thompson delivered offence, too, finally sparking broader attention for his often-unnoticed work.

"Double T," said James after Cleveland's 115-101 win, "was spectacular tonight."

Alongside James and guard Kyrie Irving, Thompson's play in Game 7 on Sunday night in Oakland will help decide whether the Warriors can seize their season's capstone or are upended by Cleveland. Thirty-three teams have trailed 3-1 in an NBA finals. Cleveland is only the third to reach a Game 7 – and the first in 50 years. No team down 3-1 in the finals has ever come back to win.

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From Toronto to Game 7

Thompson, 25, led the rush of young players from the Toronto area into the NBA. "From the first time, there was the passion," remembered Ro Russell, who coached Thompson as a teenager. "Even in warmups, Tristan went hard. He's old-school."

Playoff basketball

Thompson's performance on the offensive boards, in last spring's playoffs and again this spring, has been historic. He has averaged 4.4 offensive rebounds a game – giving his team important second chances. According to basketball-reference.com, among players with at least 30 NBA playoff games, Thompson's 4.4 is second in history, behind only Moses Malone's 5.4.

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"Be relentless on the glass," Thompson said on Thursday night. "That's my job."

And even though Thompson isn't a scorer – his career average is 9.5 points a game – his team produces offence when he's on the floor. His offensive rating, a measure of how many points are scored by a team per 100 possessions, led the NBA in the regular season and in the playoffs leads his team and is among the league's best.

Dunks

Game 6 was billed as the biggest in Cavs' history. Thompson, playing centre, won the opening tip. Later in the first quarter, Thompson took two savvy passes from James and hammered down dunks, the second putting the Cavs ahead 31-9. But Russell noted Thompson's dunks have never been showy. "When he dunks, it's because it's a high-percentage shot," Russell said. "He dunks and gets back on defence."

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Double-double

On Thursday night, the 6-foot-10 power forward piled in 11 points and snatched 10 rebounds in the first half as Cleveland surged to a large early lead. Thompson's first-half double-double was the first such performance in the finals since 2012, when Chris Bosh pulled off the feat for Miami. Thompson sealed the double-double on a smooth alley-oop dunk from a James pass.

Recognition

As Cleveland has scraped toward a never-before NBA finals victory, Thompson's work has garnered more attention. ESPN dubbed him Cleveland's "unsung hero." Deadspin called him the Cavs' "secret weapon." Cavs coach Tyronn Lue has said: "Tristan is the heart and soul of our team."

O Canada?

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Thompson has previously played national-team basketball but couldn't last summer, because he was in contract negotiations. This July, Canada, with an undermanned team missing Andrew Wiggins, has a last-shot chance to qualify for the Rio de Janeiro Summer Olympics. After the finals are over, Thompson would be a huge boost for a team that is currently helmed by a long-time friend, Toronto Raptors guard Cory Joseph.