A 20-strikeout game is one of baseball’s rarest feats.

In Major League history, there have been 23 perfect games and 18 four-homer efforts, but only five times has a pitcher fanned 20 batters while throwing no more than nine innings. (Apologies to Tom Cheney, who struck out 21 in 16 innings on Sept. 12, 1962.)

Roger Clemens recorded the first and second such performances in 1986 and '96, and Kerry Wood, Randy Johnson and Max Scherzer later added their names to the list.

Below, you'll find more on these historic outings as well as the hurlers who came up just short of the mark.

Roger Clemens, Red Sox
April 29, 1986 vs. Mariners
Sept. 18, 1996 at Tigers

April 29, 1986, was perhaps the date when the “Rocket” truly launched. Making his 40th career appearance, a 23-year-old Clemens fanned 20 of the 30 Mariners he faced and allowed one run on three hits with no walks in a complete-game win. He was the first pitcher ever to strike out 20 batters in a nine-inning game. Clemens would go on to win the first of his MLB-record seven Cy Young Awards in 1986, as well as the American League MVP Award.

A decade later, Clemens did it again in the third-to-last start of his Red Sox career. This time, the right-hander tossed a five-hit shutout against Detroit, fanning 20, walking none and throwing 151 pitches in the brilliant showing.

Kerry Wood, Cubs
May 6, 1998 vs. Astros

The highly touted Wood, who was selected fourth overall in the 1995 MLB Draft, had an up-and-down first month in the Majors, posting a 5.89 ERA over four starts in April 1998. Then came May 6, 1998, when Wood, a hard-throwing Texan in the mold of Clemens and Nolan Ryan, took the mound on a rainy day at Wrigley Field and announced his presence to the baseball world. Facing an Astros lineup that included future Hall of Famers Craig Biggio and Jeff Bagwell as well as multi-time All-Star Moises Alou, the 20-year-old righty faced 29 batters and tallied 20 strikeouts with one hit, no walks, one hit batsman and no runs allowed.

Brad Ausmus, who was catching for the Astros that day, also happened to be with the Tigers in 1996 when Clemens had his second 20-K game, and he said it was evident early on that Wood could do something special that day. “I remember thinking in the dugout, ‘Clemens struck out 20. I'm afraid this guy might strike out 27,’” Ausmus said in 2018.

Although Wood’s career achievements don’t match those of the other pitchers on this list, the right-hander’s masterpiece against the Astros is considered by some to be the most dominant pitching performance ever. In fact, his Game Score of 105 (using the Bill James formula) is the highest in MLB history for a nine-inning start.

Randy Johnson, D-backs
May 8, 2001 vs. Reds

Johnson ranks second all time with 4,875 K’s, and his gem against the Reds shows why he was such an intimidating pitcher. The 6-foot-10 left-hander carved up the Cincinnati lineup with his signature combination of an overpowering heater and a devastating slider, striking out 20 of the 29 batters he faced, walking none and allowing just one run on three hits.

Johnson, though, was unable to get the win, as the game was tied at 1-1 after nine innings. The "Big Unit" was removed after getting Juan Castro swinging for strikeout No. 20 to end the top of the ninth, and Arizona went on to win, 4-3, in 11 innings. Johnson ultimately struck out a career-high 372 batters in 2001, which is MLB’s third-highest single-season total in the modern era.

Max Scherzer, Nationals
May 11, 2016 vs. Tigers

Scherzer has assumed the mantle of baseball’s top strikeout artist among active pitchers, leading MLB in K’s by a margin of 173 with 1,851 strikeouts from 2012-18. His single-game best in that department came on May 11, 2016, vs. one of his former teams, the Tigers.

After entering the ninth inning with 18 strikeouts, the right-hander walked the tightrope in the final inning, giving up a leadoff homer to J.D. Martinez and allowing the tying run to reach base on a single by Victor Martinez after fanning Miguel Cabrera. Scherzer collected his 20th strikeout with one out remaining in the game, giving him a chance to top Clemens, Wood and Johnson with one more punchout. However, James McCann grounded out on Scherzer’s 119th pitch of the night, keeping 20 K’s as the mark to beat.

Just shy: 19-K gems

On six other occasions over the past 100 years, a pitcher has come ever so close to the record, finishing with 19 K’s in a nine-inning outing. Two of those games were thrown by Johnson, both in 1997. These are the hurlers responsible for the other four:

Steve Carlton, Cardinals
Sept. 15, 1969 vs. Mets

One of four pitchers in MLB history with at least 4,000 strikeouts, Carlton fell one K short of tying the nine-inning record in this 1969 loss to the Mets. The left-hander was never in position to record strikeout No. 20, as he fanned the side in the ninth to tally 17, 18 and 19.

Tom Seaver, Mets
April 22, 1970 vs. Padres

Like Carlton, Seaver never had a chance to pitch for his 20th strikeout in this game, as he also entered the ninth with 16 K’s and struck out the side to finish with 19.

Nolan Ryan, Angels
Aug. 12, 1974 vs. Red Sox

It’s hardly surprising to see Ryan, the all-time leader with 5,714 strikeouts and a pitcher who threw a record seven no-hitters, on this list. Ryan recorded his 19th strikeout against the Red Sox with one out remaining in the ninth, but Rick Burleson was able to put the ball in play for a game-ending flyout to avoid becoming strikeout victim No. 20. Ryan reached 19 K’s again two starts later, though that came in an 11-inning complete game.

David Cone, Mets
Oct. 6, 1991 at Phillies

Cone enjoyed an outstanding career, earning a Cy Young Award, winning five World Series titles and throwing a perfect game. He nearly added tying the nine-inning strikeout record to that list in his last start of the 1991 season. The righty opened the final inning against the Phillies with a pair of K's to reach 19, but Dale Murphy grounded out to end the game.