Both Clemens and Pedro were amazing during their time with the Red Sox, but really, I wouldn't consider either of them to be the best. They are both one of my favorite pitchers of all time but there is one other name that pops up on the list of Red Sox greats, and that's none other than the great Cy Young.
Young had already amassed more than 280 wins and had an ERA of 3.04 before joining the Red Sox, but someof his best years came while he played for them. In the 11 years prior, he had a .627 winning percentage, 1240 strikeouts, and a WHIP of 1.236. Everything changed once he joined the Red Sox and played with them for 8 years. He had a .632 winning percentage with 192 wins, which is actually tied with Clemens for the most wins in team history.
During his time before and after the Red Sox, he had an ERA under 2 just once, which was 1.93, during his 8 seasons with them, his combined ERA was 2.00, with an ERA below 2 in 5 of those seasons and a career low of 1.26 in his final year with the team. He was nowhere near being a strikeout hitter but he was amazing in every other category, heck, his career WHIP with the team is .97.
WINS: Young - 192, Clemens - 192, Martinez - 117
ERA: Young - 2.00, Martinez - 2.52, Clemens - 3.06
K's - Clemens - 2590, Martinez - 1683, Young - 1341
SHUTOUTS/20 STARTS: Young - 2.55, Martinez - 2.2, Clemens - 2
K/B: Clemens - 3.03, Young - 4.48, Martinez - 5.44
WHIP: Young - .97, Martinez - .978, Clemens - 1.158
On top of all that, Young played so much more than Clemens and martinez had, not only was Young able to throw 300 innings in a season consistantly without getting injured, he did it at a time where ther were 136 to 154 games in a season, meaning less time then now. There's a reason there's an award named after him. Overall he's known for doing so much and being one of the best in general, but some of his best moments came with Boston.
When the conversation turns to the greatest Red Sox pitcher of all time, there can only be 2 names that are involved, in my opinion. Those names are Roger Clemens and Pedro Martinez.
In the summer of 1986 Roger Clemens set the baseball world abuzz. On April 29th, 1986 he set a major league record with 20 strikeouts in one game. A feat he would repeat 10 years later, in his final season with the Red Sox. In 1986, he won the first of 7 Cy Young Awards, with a 24-4 record and a 2.48 ERA. He would also be awarded the American League MVP award that season and lead the Red Sox to their first World Series appearance in 11 years.
Over his 13 year career with the Red Sox, Clemens would win 192 games, tied for the most in club history. He would also take home 3 Cy Young Awards over that time. Clemens left the Red Sox after the 1996 season and signed a free agent contract with the Toronto Blue Jays. After leaving the Red Sox, he would win 4 more Cy Young Awards for the Blue Jays and Yankees.
Clemens retired in 2007, after 24 seasons. He would amass 354 wins, 7 Cy Young Awards, and more than 4600 strikeouts. A sure fire hall of famer, right? Well in 2007, Roger Clemens name was mentioned in The Mitchell Report. The Mitchell Report was a 409 page report detailing the investigation into the illegal use of steroids in baseball. Clemens name was mentioned 82 times in that report. According to the report Clemens use of PED's started as early as 1998, two years after he left the Red Sox.
Pedro Martinez came to the Red Sox after the 1997 season in a trade with the Montreal Expos. In only 7 years with the Red Sox, Pedro was nothing short of dominant. Pedro went 117-37 over those 7 seasons, with a 2.52 ERA and more than 1600 strikeouts in just over 1300 innings. He would win 3 Cy Young Awards in his time with Boston and finish 2nd 2 other times.
In 1999, Martínez became just the 8th modern pitcher to have a second 300-strikeout season
Martínez had perhaps his best year in 2000. Pedro posted an exceptional 1.74 ERA, the AL's lowest since 1978, while winning his third Cy Young award. His ERA was about a third of the park-adjusted league ERA (4.97). No other single season by a starting pitcher has had such a large differential. Roger Clemens' 3.70 was the second-lowest ERA in the AL, but was still more than double that of Martínez. Martínez also set a record in the lesser known sabermetric statistic of Weighted Runs allowed per 9 innings pitched (Wtd. RA/9), posting a remarkably low 1.55 Wtd. RA/9. He gave up only 128 hits in 217 innings, for an average of just 5.31 hits allowed per 9 innings pitched: the third lowest mark on record.
To appreciate these 2 pitchers though, you really needed to live through it. Clemens was great, no doubt about it. But with Pedro, it was different. There was a buzz every time he pitched. You couldn't wait to get home and watch the game on the nights he pitched. Every one of his starts had a playoff type atmosphere surrounding it. You felt that every night he pitched, something special could happen, and usually did.
For my money, Pedro Martinez is the greatest Red Sox pitcher of all time.