(Reuters) - James Harden delivered a monster debut for Houston on Wednesday with 37 points and 12 assists just hours after the Rockets stumped up the massive contract he had been seeking in Oklahoma City.

Harden, the NBA's reigning Sixth Man of the Year, was traded to the Rockets on Saturday after the Thunder balked at his demands for a contract extension.

The Sixth Man award is given to the player who makes the biggest impact for a team coming off the bench.

While Oklahoma City were reluctant to invest so heavily in Harden, Houston did not hesitate and reached a five-year deal worth roughly $80 million with the new cornerstone of their franchise.

Harden showed why the Rockets splashed the cash in a season-opening 105-96 win over Detroit, exploding for a big scoring night and having a career-high in assists.

After playing a supporting role to Kevin Durant and Russell Westbrook in Oklahoma City's run to last season's NBA Finals, Harden is now the leading man in Houston.

"It's a new role for me. I think everybody knows that," Harden told reporters. "My job is just to do the best I can every day. I just have to be a leader out there."

The Rockets clearly think he can be that leader.

"James Harden is the foundational-type player we have been looking to add," said Rockets owner Leslie Alexander. "He is ready to make the next move up to join the elite players in the NBA."

(Writing by Jahmal Corner in Los Angeles; Editing by Peter Rutherford: jahmalcorner@gmail.com)