Q. Misiorowski's 103.5 mph first pitch: what World Series record did he break?

The 2026 World Series was one pitch old when it produced a record. Milwaukee Brewers starter Jacob Misiorowski opened Game 1 with a fastball clocked at 103.5 mph, and the headlines called it the fastest pitch in World Series history. Read a little further, though, and a qualifier appears: since 2008. So what record did he actually break?

The short answer: Misiorowski’s 103.5 mph (about 166.6 km/h) fastball is the fastest pitch thrown in any World Series since MLB’s pitch tracking began in 2008. The previous high was 103.2 mph, thrown by Aroldis Chapman of the Chicago Cubs in Game 2 of the 2016 World Series.

What happened on the first pitch of Game 1?

Game 1 was played on Friday night, 23 October, at American Family Field in Milwaukee. Misiorowski’s first pitch, to Tampa Bay Rays leadoff hitter Yandy Díaz, was a four-seam fastball, the basic straight fastball. It flew high over the strike zone for a ball, but that makes no difference to the record. A velocity mark only measures how fast the ball was thrown, not where it ended up.

The Brewers won 3-2. Misiorowski lasted five innings, giving up one run on four hits and one walk with three strikeouts, and threw 78 pitches. It was the first postseason win of his career. He led the majors in both strikeouts (252) and ERA (1.80) during the regular season, according to MLB.com. ERA, or earned run average, is the number of earned runs a pitcher allows per nine innings.

How fast is 103.5 mph in km/h?

US baseball measures pitch speed in miles per hour. A mile is exactly 1.609344 kilometers, so 103.5 mph comes to about 166.6 km/h, and Chapman’s 103.2 mph to about 166.1 km/h. The gap between the two pitches is 0.3 mph, or roughly half a kilometer per hour.

Here is a rough estimate of our own to show what that speed means. The pitching rubber sits 60 feet 6 inches (18.44 m) from home plate, but pitchers stride toward the plate and let go of the ball several feet in front of the rubber. Assume the ball leaves the hand about 54 to 56 feet (16.5 to 17 m) from the plate and keeps its full speed the whole way, and it arrives in 0.36 to 0.37 seconds. A real pitch loses a little speed to air resistance, so it takes slightly longer. Either way, the ball reaches the plate in less than four-tenths of a second. That is our back-of-the-envelope figure, not an official measurement.

In that sliver of time a batter has to decide whether to swing and get the bat moving. How anyone manages it is one of the explainers that branch out from this story.

Why does the record only count from 2008?

“Since 2008” marks the period for which comparable numbers exist. MLB’s pitch-tracking data goes back to 2008, and MLB.com describes Misiorowski’s pitch as the fastest in the World Series since then. Earlier World Series pitches were not measured by the same system, so they cannot be lined up against it on equal terms. That is why Yahoo Sports was careful to call it the fastest pitch in the “recorded” history of the Fall Classic, as the World Series is also known.

There is a second point that is easy to miss. This is the fastest pitch in a World Series, not the fastest pitch in MLB (Major League Baseball) history. Faster pitches have been recorded in regular-season games. Here is how the two World Series marks compare.

Detail	Misiorowski, 2026	Chapman, 2016
Speed	103.5 mph (about 166.6 km/h)	103.2 mph (about 166.1 km/h)
Game	World Series Game 1, first pitch	World Series Game 2
Team	Milwaukee Brewers	Chicago Cubs
Role	Starting pitcher	Closer

The roles differ, too. Chapman was the Cubs’ closer, a pitcher who usually works near the end of a game. Misiorowski is a starter, who is expected to last several innings, and he set the mark with the very first pitch of the night.

Who is playing, and when are the next games?

The Milwaukee Brewers, champions of the National League, face the Tampa Bay Rays, champions of the American League. Neither franchise has ever won the World Series, so 2026 is guaranteed a first-time champion. Milwaukee is back for the first time since 1982, when it lost a seven-game series to the St. Louis Cardinals. Tampa Bay is making its third appearance, after losing to the Philadelphia Phillies in 2008 and the Los Angeles Dodgers in 2020.

The series is best of seven, so the first team to win four games takes the title. Milwaukee went 103-59 in the regular season, better than Tampa Bay’s 98-64, and holds home-field advantage: Games 1, 2, 6 and 7 are in Milwaukee. Games 3-5 are scheduled for 26-28 October at Tropicana Field in St. Petersburg, Florida, and Games 6 and 7 for 30-31 October back in Milwaukee. Games 5, 6 and 7 happen only if they are needed, and from Game 3 on, first pitch is set for 8 p.m. ET.

What do the words in this story mean?

This site saves one news story at a time and branches out into the words inside it. These are the first ones worth knowing.

Word	What it means here
mph	Miles per hour, the unit US baseball uses for pitch speed. 103.5 mph is about 166.6 km/h
Velocity and Statcast	Velocity is how fast a pitch is thrown. MLB clocks every pitch with Statcast, a tracking system installed in its ballparks
World Series	MLB’s championship series between the American League and National League winners. Only US and Canadian teams take part, yet it is called “World”
Reaction time	The time between seeing something and moving in response. A batter gets less than 0.4 seconds from release to plate
Tommy John surgery	An operation that rebuilds a damaged ligament on the inner side of the elbow with a tendon taken from elsewhere. It is named after the first pitcher to have it

Each word gets its own explainer, one a day, listed under “Branching out from this story” below.

In short

Misiorowski’s 103.5 mph (166.6 km/h) first pitch in Game 1 is the fastest thrown in a World Series since pitch tracking began in 2008, edging Chapman’s 103.2 mph from 2016. It is not the fastest pitch in MLB history, and the series between two clubs chasing their first title can run until 31 October.