On this date in 1998, Chicago Cubs rookie Kerry Wood tied the major league record with 20 strikeouts. It looked like this:

It may have been the most dominant major league game ever pitched. By game score, it's the best in history. He gave up one infield hit and issued no walks (although he did hit one batter, which isn't counted in game score). For the quality of his stuff that day, check out curveballs at the 50-second mark to Jeff Bagwell and at 1:25 to strike out Dave Clark.

Astros fans may point out that it was a cloudy, gray afternoon and visibility wasn't great. Plate ump Jerry Meals may have had a generous strike zone that day (Astros starter Shane Reynolds had 10 strikeouts).

Of course, it takes a special confluence of events for a pitcher to strike out 20 guys in a game, beyond explosive talent. That's why it has happened only three other times in a nine-inning game.

Roger Clemens, April 29, 1986

This was the young Clemens, relying on a high fastball and curveball; the splitter would come later. Plate ump Vic Voltaggio appeared to help a bit; check him out ringing up Al Cowens at the 45-second mark and Ivan Calderon at 1:30. Still, Clemens simply blew his fastball past the helpless Mariners that night. That was also a team in the midst of an unbelievable strikeout slump: They'd struck out 18 times against the A's 10 days earlier and in a nine-game span around the Clemens game, struck out 16, 11, eight, 12, 20, 16, five, 13 and 10 times. They set the American League record for strikeouts in a season (since broken). "He was awesome, just awesome," Red Sox catcher Rich Gedman said of Clemens after the game. "None of the Mariners said anything. They looked like they wanted to say something, but they didn't know what to say."

Roger Clemens, September 18, 1996

This was an older Clemens, in one of his final games with the Red Sox, a little thicker around the waist and with an extra chin. He still threw hard but didn't rely so much on a high fastball, with a lot of the strikeouts coming via the splitter, like the one to Tony Clark at 2:10. That was a terrible Tigers team that lost 109 games and led the AL in strikeouts. That game was the 11th of 12 consecutive losses. They'd had 17- and 14-strikeout games earlier in the streak and had fanned 13 times the night before.

Randy Johnson, May 8, 2001

This was pure power, of course. This doesn't seem to be remembered like the Wood game or the first Clemens game, perhaps because Johnson didn't win it -- he left after nine innings with the game tied 1-1. The Reds had a pretty weak lineup that night, with several bench guys playing (I'm guessing a few regulars called in sick): Donnie Sadler hitting leadoff, Juan Castro batting second, Alex Ochoa in the cleanup spot, Ruben Rivera -- career strikeout rate of 28 percent -- hitting sixth. The Reds lost 96 games that year and finished third in the NL in strikeouts.

****

Johnson's game came 15 years ago. The interesting thing is this: Strikeouts have continued to rise since then, but no pitcher has tied -- let alone broken -- the record. Strikeouts per game have risen from 6.67 in 2001 to 8.00 in 2016. Those '86 Mariners struck out 1,186 times -- a mark that has been exceeded 138 times since 2002, with last year's Astros striking out 1,535 times. Still, since Johnson's game we haven't even witnessed a 19-strikeout game and have had just two 18-strikeout games (Ben Sheets of the Brewers in 2004 and Corey Kluber for the Indians last year).

So why haven't we seen the record matched? A few reasons:

1. Pitch counts. Clemens threw 151 pitches in his second 20-strikeout game, 138 in his first game, Johnson threw 124 pitches and Wood 122. Pitchers rarely are allowed to throw 120 these days. The best example of this is Kluber. His 18 strikeouts came in just eight innings, but he'd thrown 113 pitches and Terry Francona brought in a reliever for the ninth. Johan Santana fanned 17 in eight innings in 2007 for the Twins but was removed after 112 pitches; that also was a 1-0 game, which perhaps dictated bringing in the closer rather than letting Santana go for the record. Anibal Sanchez of the Tigers also fanned 17 in eight innings in 2013, but left after 121 pitches.

It's difficult to strike out so many batters and be efficient. When Vince Velasquez struck out 16 in April, he didn't walk anybody and gave up just three hits, but still threw 113 pitches. Max Scherzer had a 17-strikeout no-hitter against the Mets with no walks last October and threw 109 pitches. It's difficult to be more efficient than that and still rack up the K's. So unless a manager is willing to let a pitcher get near 130 pitches, it's going to be difficult to get to 20 strikeouts.

2. Batters are more used to velocity. Young Clemens simply blew guys away with a fastball that few batters had seen back then. Wood, with his upper-90s fastball and wipeout curve and slider, was a phenomenon that rookie season. Johnson was obviously unique. But now we see more guys throwing 95 mph, so while strikeouts are up, hitters are also more used to seeing high octane on a regular basis. Maybe that makes it more difficult for any one pitcher to dominate on a single-game basis.

3. The strike zone. We know the strike zone has expanded in recent years -- but it's expanded at the bottom (although that expansion finally stalled last season). Strikeouts with fastballs happen more often at the top of the zone or on the sides of the plate, not at the bottom. Clemens and Wood probably benefited from a wider zone than today's pitchers, who benefit from a zone that is now more horizontal. That type of zone also has led to pitchers -- even those with good fastballs -- throwing more two-seamers, which can be less of a swing-and-miss pitch than a four-seamer in the zone.

After the Mariners lost that game to Clemens, designated hitter Gorman Thomas said, "I think we all should be happy we were here, because I don't think we'll ever see that again. I know I'll never see it again for as long as I live."

Well, Gorman was wrong about that. And I suspect we'll see another 20-strikeout game. It just may take a game in September, against a team mailing it in and playing a lot of subs, with an umpire with a little wider zone that night, and a manager willing to extend the pitch count an extra 10 or 15 pitches. Because there's no doubt that with all these great pitchers today that somebody has the talent to pull it off.