The A’s are building up their minor-league options this winter, and while their bullpen was solid down the stretch of the 2025 campaign, posting a 2.99 ERA from August through the end of the season, they’re also an inexperienced group.

On Thursday, they added a little more experience in signing former New York Yankees pitcher Geoff Hartlieb. The righty is set to turn 32 next month, and was signed by the Yankees last winter, racking up 35 innings in Triple-A with Scranton/Wilkes-Barre, holding a 3.34 ERA with a 1.29 WHIP in that span. He was also striking out 26.2% of the batters he faced and walking just 6.9%.

Hartlieb did get a look in New York in early July, making two appearances in pinstripes and totaling 1 1/3 innings of work with six earned runs allowed, four walks and four strikeouts. He would be designated for assignment that same month, and ended up signing with the Detroit Tigers, where he would get another look in the big leagues.

The righty made another two appearances with the Tigers, tossing two innings and holding a 9.00 ERA. In that brief time he gave up three hits, walked a pair and struck out one. Detroit would release him towards the end of August, and he ended up singing with the Kansas City Royals, where he finished the season in the minors.

One standout number for Hartlieb year-over-year is that his slider usage in the big leagues went from 18.8% and a fourth pitch, to his most-used offering in his four appearances, sitting at 60% usage. He also dropped his cutter from 2024 and primarily focused on his slider/four-seam combo while working in a sinker as well.

Another interesting tidbit with Hartlieb is that his velocity was down more than two full ticks on his fastball in his time in the big leagues, going from 97.1 miles per hour in 2024 to 94. 9 mph in his four appearances this past season.

In his final appearance of the season as a member the Omaha Storm Chasers, that velocity had rebounded a little bit, sitting at 95.7 mph, which is a 0.7 mile per hour increase over his average on the season. His slider was also up in velocity, sitting at 86.2, up from 85.6. That one had been up at 87 miles per hour the previous year.

Given his results in the big leagues this past season, the fact that he bounced from New York to Detroit to Kansas City in 2025, and that his velocity was well down this season, this is an interesting pickup for the A’s. Perhaps this is just a depth pickup where they’re just looking to fill out the Triple-A bullpen.

Or maybe there is something in his profile where they feel his slider, which had a 37.5% whiff rate, can be a dominant pitch for him in 2026 while figuring out the right mix for his second and third offerings.

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