MESA, Ariz. -- For almost the Athletics' entire history, ace left-handers have driven their greatest successes.
Hall of Famers Eddie Plank and Rube Waddell delivered the franchise's first pennant in 1904, and Plank helped win four American League titles and three World Series championships from 1910-14. Arguably the best southpaw of all time, Lefty Grove spearheaded three pennants and two World Series titles from 1929-31. Vida Blue and Ken Holtzman were key cogs in three consecutive World Series victories from 1972-74.
COMPLETE ATHLETICS PROSPECT COVERAGE
The A's three straight pennants from 1988-90, including another championship in 1989, are the lone exception. But their last two 100-victory clubs, in 2001 and 2002, featured Mark Mulder and Barry Zito. And as they try to get back to contention after averaging 98 losses during the last four seasons, lefties may provide the key.
Behind budding superstar shortstop Leo De Vries, the A's best prospects are southpaws Jamie Arnold, Gage Jump and Wei-En Lin. Arnold unexpectedly fell to them with the 11th pick in the 2025 Draft, while Jump was an over-slot second-rounder in 2024 and Lin landed the largest bonus ($1.13 million) given to any pitcher in the 2024 international class. Arnold has yet to appear in an official game but could be on an even faster timetable than Jump and Lin, who reached Double-A in their 2025 pro debuts.
The A's will have Arnold open the season in Double-A, making him their first pitcher to do begin his first full year as a pro at that level since 2011 first-rounder Sonny Gray. A two-time All-American at Florida State, he unleashes 93-96 mph fastballs and wipeout 82-85 mph sliders from an unusual angle. His mid-80s kick change will become a weapon once he learns to harness it.
"Jamie is a unique mover down the mound with an unusual slot," director of player development Ed Sprague said. "He gets compared to Chris Sale a little bit. The quality of his three-pitch mix and outlier delivery makes him unique. There's not really much to do with him, just manage his innings."
After operating at 90-95 mph with quality carry as a redshirt sophomore at Louisiana State, Jump averaged 95 mph and touched 98 regularly last season. His low-80s slider works better than his upper-70s curveball, and he's refining two versions of a changeup, a kick change to get chases and a regular cambio to elicit grounders. He posted a 3.28 ERA, .214 opponent average and a 131/34 K/BB ratio in 112 2/3 innings between High-A and Double-A in 2025.
"We were surprised a little bit by Gage's velocity jump," Sprague said. "We did some delivery cleanup stuff with him but not a ton. He has a good changeup and the big thing in his development has been throwing his changeup more. He has a cutter now that goes in on right-handers and the increase in velocity has made his breaking balls better. "
Lin climbed from Single-A to Double-A at age 19, compiling a 3.72 ERA, .217 opponent average and 117/22 K/BB ratio in 87 innings. Extremely advanced for his age, he throws six different pitches that each show solid potential: a lively low-90s four-seamer, a mid-70s curveball, a low-80s sweeper, a tighter with similar velocity, an upper-70s changeup and a low-80s splitter. He pitched in both the World Baseball Classic and big league camp this spring.
"For a young kid, Lin is really impressive," Minor League pitching coordinator Barry Enright said. "He's only going to get stronger, which is going to stabilize his delivery and his consistency. I think his changeup is going to be a weapon. He has the weapons and the mentality to execute."
Camp standout: Leo De Vries (No. 1 prospect)
No. 4 on MLB Pipeline's Top 100 Prospects list and No.1 on the Athletics' Top 30 Prospects list, De Vries has made that ranking look perhaps too conservative this spring. Still just 19, he showed off his 30-30 potential in Cactus League action, slashing .426/.460/.723 with three homers and four steals in 18 games. He also made a nifty defensive play and displayed a strong arm at shortstop during the A's Spring Breakout victory over the Brewers.
"Leo has an it factor about him," Sprague said. "The stage was not too big for him being in big league camp. There's a lot to love. It's just a matter of cleaning up a few things defensively."
Breakout potential: Breyson Guedez (No. 23 prospect)
Signed for $1.5 million out of Venezuela in 2025, outfielder Breyson Guedez broke into baseball by batting .359/.395/.490 in the Rookie-level Dominican Summer League at age 17. He's so advanced at the plate that the A's will jump him to Single-A for his debut this season. They gave him a taste of Cactus League play and he blasted a 450-foot home run off big leaguer Michael King, and he also drilled a 425-foot homer during Spring Breakout.
"He has the bat and power, an accurate and strong arm and he gets good jumps and reads," Sprague said. "He's more of a corner guy but he just has a knack at the plate. There are some Rafael Devers comps."
Bounceback candidate: Steven Echavarria (No. 16 prospect)
One of the top high school right-handers in the 2023 class, Steven Echavarria received first-round money ($3 million) after the A's floated him to the fourth round. Though he can run his fastball up to 99 mph and flash a mid-80s slider with depth, he owns a 5.29 ERA with 78 walks in 161 2/3 pro innings. He did make progress in High-A last season and has done a better job understanding his delivery and landing his secondary pitches in the strike zone this spring.
"I think Steven's ready to break out," Sprague said. "He has struggled with command and wouldn't have enough pitches to get through an outing. He throws some nasty sliders. He's up to 98-99 mph, so he has the fastball. I'm excited for him this year."
Draft sleeper: Bobby Boser (No. 30 prospect)
After spending his first three college seasons at South Florida, Bobby Boser transferred to Florida and hit .336/.437/.613 with 18 homers and 19 steals last spring, making him one of the more desired college seniors in the 2025 Draft. The A's were able to get him with an 11th-round pick and a $150,000 bonus. He could have average tools across the board to go with the savvy that allowed him to play every position but catcher and pitcher during his amateur days.
"Bobby plays a really good shortstop and he can play third base too," Sprague said. "He has a little thump and runs well. After watching him play, I don't know how an SEC shortstop like that gets to the 11th round."