Looking back over four-plus decades of Blue Jays baseball, many of the eras are defined by which ace was leading the staff.

Dave Stieb was the Blue Jays' workhorse star in the 1980s, leading the rotation as Toronto rose from an expansion team to a competitor. The Roy Halladay years are an era all of their own, too. Though those years might have lacked team success, they featured some of the game’s best pitching for parts of 12 seasons. In between, there was Roger Clemens’ often-forgotten trip north for two dominant seasons.

Here are the best individual seasons by Blue Jays pitchers:

1. RHP Roger Clemens -- 1997
Clemens’ 1997 season stands above all others in Blue Jays history -- hitters included -- with 10.7 WAR. Forget Blue Jays history for a moment. In the Live Ball Era (since 1920), only three pitchers -- Pedro Martinez (1999), Steve Carlton (1972) and Bert Blyleven (1973) -- have produced a higher WAR over a single season.

Clemens’ numbers that season were foolish, going 21-7 with a 2.05 ERA over 34 starts (264 innings), including nine complete games, three of which were shutouts. This was the first of back-to-back American League Cy Young Awards for Clemens, who went 20-6 with a 2.65 ERA with the Blue Jays in '98. Those were another two seasons outside of the playoffs for the Blue Jays in a stretch of years that seem to blur together, and Toronto fans have rarely claimed Clemens as one of their own, but that '97 season still stands as the best single-season pitching performance the club has produced.

2. RHP Roy Halladay -- 2003
This list isn’t complete without the great Halladay, whose excellent 2003 season earned him his first AL Cy Young Award at age 26. Halladay’s career was more about sustained dominance than peak seasons, but '03 best encapsulates what made him special.

Halladay made 36 starts that season, throwing 266 innings with nine complete games (two shutouts), something we simply don’t see any more. He won 22 games and was able to work deep so consistently because he walked just 32 batters all season, an incredible accomplishment. There were years in which Halladay had lower ERAs than his 3.25 in '03, and his final two seasons in Toronto (2008-09) also deserve respect, but '03 is the whole package.

3. RHP Roger Clemens -- 1998
Clemens’ second season in Toronto was nearly as good as his first, which was a high bar to live up to. Clemens pitched fewer innings (234 2/3), but posted another 20-win campaign with a 2.65 ERA and higher strikeout rate (10.4 K/9) than the season prior. At 8.2 WAR, Clemens' '98 season was worthy of a second consecutive AL Cy Young Award.

The '98 season also featured one of the best stretches of pitching we’ve seen, when Clemens strung together three consecutive shutouts -- Aug. 20 against the Mariners, Aug. 25 against the Royals and Aug. 30 against the Twins. The middle game was Clemens' 18-strikeout classic, and he carried that momentum into September, when he recorded double-digit strikeouts in four of his last five starts. While Clemens’ individual record was 20-6, the Blue Jays went 24-9 in his starts.

4. RHP Roy Halladay -- 2009
Halladay’s 2008 and '09 seasons were very similar, with ERAs of 2.78 and 2.79, respectively, but let’s give his final season with the Blue Jays the slight edge. With an ERA+ of 159 and one of his best seasons for limiting walks (1.3 BB/9), Halladay went out in style with the Blue Jays and deserved better than his fifth-place finish in AL Cy Young Award voting.

Halladay’s peaks were incredible, but his consistency from season to season while throwing so many innings is what made Doc special. The '09 season featured another nine complete games for Halladay, four of which were shutouts, a career high for him with the Blue Jays. Halladay threw 100-plus pitches in 26 of his 32 starts, including each of the final 17.

5. RHP Dave Stieb -- 1984
No list of Blue Jays pitching achievements is complete without Stieb, the franchise great whose excellence in the 1980s remains underappreciated.

Stieb’s '85 season featured a 2.48 ERA, and he was dominant through the early '80s, but '84 splits the middle to present the complete package of Stieb. That season, the right-hander went 16-8 with a 2.83 ERA over 267 innings, which included the best strikeout rate of his career (6.7 K/9).

Many Blue Jays fans associate 10-inning starts with Halladay, but prior to Doc, it was Stieb carrying that heavy load. He did that once in '84, throwing 10 innings in a 4-3 win over the Royals at Exhibition Stadium on May 4. Stieb threw fewer than seven innings just five times in 35 starts and went the distance 11 times.

Honorable mentions
This list excludes two Cy Young Award winners in Pat Hentgen (1996) and Robbie Ray (2021), showing just how strong the Blue Jays’ front-end pitching has been over the years. Ray’s dominant 2021 campaign nearly cracked the top five after he posted a 2.84 ERA with 248 strikeouts over 193 1/3 innings. The top seasons from Jimmy Key and Juan Guzman have fine cases of their own, too.

2021 Ray -- 13-7, 2.84 ERA (3.9 WAR)
2008 Halladay -- 20-11, 2.78 ERA (6.7 WAR)
2002 Halladay -- 19-7, 2.93 ERA (6.8 WAR)
1996 Hentgen -- 20-10, 3.22 ERA (6.0 WAR)
1992 Guzman -- 16-5, 2.64 ERA (5.5 WAR)
1987 Key -- 17-8, 2.76 ERA (5.6 WAR)
1985 Stieb -- 14-13, 2.48 ERA (4.5 WAR)
1983 Stieb -- 17-12, 3.04 ERA (5.1 WAR)