Roger Clemens, the volatile two-time Cy Young winner, Friday signed a four-year contract extension with the Boston Red Sox estimated at $20 million, making him the highest paid player in baseball.

Clemens' average salary of $5 million a year surpasses the $4.7 million average for five years signed by Oakland outfielder Jose Canseco prior to the 1990 season, and the $4.05 million deal free agent Darryl Strawberry signed with the Los Angeles Dodgers in November.The Clemens' extension runs from 1992 through '95, with an option for 1996. He was in the last year of a three-year contract.

The right-hander known as the "Rocket" was 21-6 last season with a major-league leading 1.93 ERA, striking out 209 in 228 innings despite a shoulder injury that limited him to two starts in September.

His total strikeouts ranked fourth in the American League. Already the Red Sox all-time strikeout leader with 1,424, Clemens is the only Boston pitcher with five 200 strikeout seasons and raised his club record of 10-strikeout games to 41.

He also boasts the team's all-time winning percentage of .695 with a 116-51 record.

"We are all delighted to get this contract finished," Boston General Manager Lou Gorman said. "Roger is obviously a very important member of this ballclub and this is a big step toward keeping the Red Sox winning over the next five years.

"He is not only one of the best pitchers in Red Sox history, but the premier pitcher in basseball today," Gorman said. "We look forward to seeing him in a Boston uniform for many years to come."

Clemens also could be the most controversial. He has been fined recently for an altercation in a Houston bar, and for cursing at umpire Terry Cooney in the fourth and final game of the American League Championship Series.

The deal comes one day after the Red Sox inked left fielder Mike Greenwell to a 4-year contract worth $12 million. Boston also reached an agreement with Tom Brunansky this week, signing him to a 3-year deal with incentives that could boost it to $9.1 million.