If there is one storyline that the 2021 season will be remembered for, it will be the league’s midseason crackdown on foreign substances, commonly referred to as “sticky” by players and coaches.

Players utilized various non-approved substances to manipulate spin rates and the resulting movement of their pitches. More movement, in a vacuum, results in more swing and miss. But the league had incentive to ban the use of any non-rosin substance in order to counteract the seemingly endless inflation of strikeout rates across the league. After the enforcement, players lamented the removal of sticky, citing issues with the slipperiness of the current major league baseball.

The national attention around the sticky substance saga may have peaked this season, but the full picture has yet to come into focus. The chapter we’re on right now takes us to the Arizona Fall League (AFL), where MLB is testing a tacky substance that is pre-applied to balls before use. The result is a subtle increase in the friction between skin and the baseball. 

Two of the Cubs top pitching prospects, Caleb Kilian and Ryan Jensen, have had a chance to throw these pre-tacked baseball for the first time. But they’re also throwing a major league baseball for the first time.

In 2019, the Triple-A level of Minor League Baseball began using major league baseballs instead of minor league baseballs. The result was a massive increase in offensive output. As Baseball America put it, from 2001 to 2018 the most home runs a single Triple-A team hit was 200. In 2019, half of the Triple-A level hit 200 or more home runs. As of this past season, the Triple-A level still uses major league baseballs.

Some pitchers are affected by the feel of the major league baseball compared to the minor league ball when they make the Double-A to Triple-A leap. Major league baseballs are manufactured in Costa Rica while minor league baseballs are manufactured in China. Minor league baseballs also have slightly different leather and larger seams.

“I’ve maybe thrown [a major league baseball] a few times, but I didn’t realize how different they were until I started pitching with them,” Kilian said. “I feel like they make my pitches move more.”

The AFL uses major league baseballs and is made up of players from various levels. Players who do not have Triple-A experience before going to the AFL are using the major league baseball in-game for the first time.

As mentioned above, the AFL is also testing a pre-tacked baseball. However, these didn’t arrive in the AFL until after the second week of the season.

In Ryan Jensen’s first start in the AFL on Oct. 14 with the standard, un-tacked major league baseball, he walked 4 batters in 1.1 innings. This was a lack of control he’d only shown one other time in 20 starts this season.

“I was definitely struggling with [the major league baseball] to start,” Jensen said. “It was very slick, even rosin didn’t help that much… It felt like I was throwing a cue ball.”

In Jensen’s next two starts combined, he went 8 innings, struck out 5 and allowed only 3 walks. These outings came with the pre-tacked baseball the AFL is testing.

“I’m a big fan of them,” Jensen said. “They’re a lot better.”

Kilian experienced a similar lapse in control during his first outing in the AFL. He walked just one batter but allowed 7 earned runs on five hits and didn’t record an out. In his last two AFL outings, Kilian has gone 7 innings, allowing just 3 hits and striking out 11 batters with no walks. Kilian also received the AFL award for Player of the Week after his stellar performance during the third week of the AFL season.

MLB also tested these pre-tacked baseballs in the final weeks of the Triple-A season, choosing a select number of teams to use the novel balls. The use of these pre-tacked balls in the AFL seems to be expansion of the idea, perhaps to gather more data on the in-game performance of the ball.

There are still some difficulties that the AFL is trying to sort through. For one, Jensen said the substance applied to the balls rubs off with relative ease. While this wouldn’t be a major issue at the major league level given how frequently balls are thrown out of play, in the AFL, games are currently limited to 7 boxes of pre-tacked balls. Once the allotment is used, balls are recycled to get through a game.

It remains to be seen whether MLB expands the use of pre-tacked baseballs to the major league level next season. An alternative would be to expand the use of the pre-tacked balls to spring training in order to obtain more player feedback at the major league level before finalizing a change.

For Kilian and Jensen, something as simple as what ball they will be throwing next year is still up in the air. If they both start at Double-A, each will revert back to throwing the standard minor league baseball they both threw most of the 2021 minor league season. If either start at Triple-A, they will be using a major league baseball, but it’s unknown at the moment whether the league will expand the use of pre-tacked balls to every Triple-A team. 

The positive, however, is that both pitchers have now had experience throwing a minor league baseball, a major league baseball and these experimental pre-tacked major league baseballs.