With alternate sites coming to an end, MLB Pipeline is recapping the development highlights for the prospects involved for each organization.

Top position prospect: Jarred Kelenic, OF (No. 1 on Top 30)
Kelenic started knocking on the big league door during Summer Camp and didn’t stop throughout his time at the alternate site in Tacoma. He continued to make hard contact and hit for a ton of power while running and defending well. The Mariners continued to push him to take on more leadership responsibilities, and the 21-year-old was up for the challenge.

“Over the course of 2019, we saw with our own eyes how talented he was on the field,” Mariners farm director Andy McKay said. “Coming into 2020, and certainly into the alternate site, we challenged him in terms of leadership and leading by example, relationship development with teammates, creating influence, modeling behavior. He took it and ran with it. In an organization with a lot of guys who work hard, he sets the example with the way he goes about his business, the competitiveness he gives to every drill, the desire to be great and help us win.”

After Kelenic made it to Double-A and turned in a 20-20 performance in his first full season of pro ball, many wanted to see the Mets’ 2018 first-round pick out of the Wisconsin high school ranks -- he was traded to the Mariners in the Robinson Canó deal -- in the big leagues this season, especially given Seattle’s current youth movement. But given that he had just 92 plate appearances above Class A ball on his resume, the Mariners were going to err on the side of caution.

“For a guy with as few at-bats at the Double-A level, we were trying to be disciplined,” McKay said. “He basically missed a year of development, and to throw him into the mix wasn’t a risk we were willing to take. We believe he’s going to be a cornerstone player for us for a long time.”

Top pitching prospect: Logan Gilbert, RHP (No. 4)
Gilbert, the Mariners’ first-rounder in 2018, traveled the same route as Kelenic in his first full year, pitching across three levels and finishing by pitching very well in Double-A in 2019. If this summer has shown anything, Gilbert is just about ready to contribute to the big league rotation, just like rookies Justus Sheffield and Justin Dunn did in 2020. The 6-foot-6 right-hander used the time to particularly work on his changeup early, then to refine his overall arsenal.

“When we were in Summer Camp 2.0, he showed he had the ability to be on that mound and in that stadium,” McKay said of Gilbert’s time in Seattle. “As we went down to alternate site, he continued to work and fine tune things as far as pitch usage, sequencing, when to go after a hitter’s hole or go to your strength. There was a stretch when he couldn’t have pitched better as far as pure stuff and command. When your best pitching prospect is your most diligent and focused worker, it’s quite a combination.”

Youngest prospect: Noelvi Marte, SS (No. 7)
When the decision was made to bring the 18-year-old Marte to the alternate site, there weren’t high expectations about how he would swing the bat. Sure, he hit an impressive .309/.371/.511 in 2019, but he’s yet to play a professional inning in the United States. So there were definite offensive growing pains, but he was able to really work on his glovework while showing glimpses of all of his tools.

“He certainly had his struggles at the plate at times,” McKay said. “The defense, we were really able to work on that. [Mariners infield coach] Perry Hill helped virtually. He made tremendous strides there. Even when he had a tougher day, older players kept commenting, ‘Wow.’ The power is real. The arm is real. The defense is real. The run is real.

“He was playing in an alternate site environment out of the Dominican Republic. He’s a very exciting player. He struggled, but he never wavered. Everything you needed to see, you saw pretty consistently.”

2020 Draft picks
Four of the Mariners’ six new draftees (Connor Phillips and Taylor Dollard were not there) got their careers unofficially started in Tacoma this summer and the Mariners were impressed with how they all began their transition from college to pro ball. Second-rounder Zach DeLoach (No. 12) fit right into Summer Camp and at the alternate site, hitting in the middle of the lineup with Kelenic and Cal Raleigh. And third-rounder Kaden Polcovich (No. 29) was often the talk of the site.

“Polcovich really stood out how quickly he worked his way into the lineup,” McKay said. “The grittiness, there were comps to Donnie Walton as an Oklahoma State, second base type. If you were to ask the players and staff who was the guy you’d trust the most, his name came up all the time. He’s a [Dustin] Pedroia-ish little-guy-who-plays-big type, who’s not afraid of anything.”

On the pitching side, the Mariners were obviously excited to work with top pick Emerson Hancock (No. 3), though the looks were somewhat limited. The right-hander, who was taken No. 6 overall, had some very minor tenderness and the Mariners were understandably moving forward with an abundance of caution. Then he was finally ready to go and extenuating circumstances interfered.

“The day he threw in the game for the first time, the smoke came in,” McKay said. “He threw and we sat there for 10 days, smoked out. But he’s really exciting. He’s a very mature person and he gravitated toward Logan.

“The stuff is undeniable. He’s a high IQ guy who is a very thoughtful, focused worker who thinks about what he’s doing out there.”

Pleasant developments
Catcher Cal Raleigh (No. 8) continues to be, according to the Mariners, one of the most underrated prospects in the game. The third-round pick in 2018 hit 29 homers and threw out 30 percent of potential basestealers in his first full season, reaching Double-A in the process. He swung the bat really well all summer and has a very high floor.

Keep an eye on Logan Rinehart. He’s not currently on the Top 30, but could work his way on in 2021 based on how he’s performed this summer. A 16th-rounder in 2019 out of California Baptist University, the right-hander pitched his way to full-season ball during his debut summer, then showed up to Spring Training in exceptional shape. His work has paid off and McKay thinks he could really break out during the current developmental fall league program in Peoria.

“It’s been electric stuff since February, upper 90s fastball with a changeup,” said McKay, who added Rinehart will continue to focus on refining his breaking stuff. “He was the talk of Spring Training, then COVID hit.”