TORONTO — How Toronto Blue Jays GM Ross Atkins goes about piecing together the 2020 rotation will be the biggest storyline between now and next March 26 when the Boston Red Sox show up on opening day.

With the position player pieces starting to fall into place this season, starting pitching will be the difference between a legitimate competitive window opening and years of sitting in the middle of the pack, where most of baseball resides.

It’s not a unique problem.

Pitching wins games, pitching gets paid, and good pitching is really, really hard to find.

Atkins has talked up the depth he’s been able to acquire over the last year or so, and some of those arms have been given a chance lately.

There’s also another wave coming over the next calendar year, one that includes a pair of recent first-round picks — 2016 first-rounder T.J. Zeuch and the 28th overall pick in the 2017 draft, Nate Pearson — who are currently putting the finishing touches on their development in Triple-A.

Things will change this winter via free agency and/or the trade market, but let’s take a look at the long list of names that will arrive in Dunedin next February looking to stake claim to a 2020 rotation spot.

RHP Trent Thornton

2020 age: 26

Key stat: 30.7 per cent ground-ball rate

Now that Marcus Stroman is in Queens, Thornton has been the Jays’ most valuable starter this season, posting 1.3 fWAR through 25 starts.

It’s been an up and down season for the right-hander who was acquired last winter from the Houston Astros in exchange for utility infielder Aledmys Diaz.

On occasion, Thornton walks too many. Sometimes, he’s homer prone, and the aforementioned ground-ball rate is scary in the American League East.

When the Blue Jays do contend, most see Thornton and his funky delivery and his high spin rate breaking ball in a setup role, but he’ll get another chance in 2020 to prove he can stick in the rotation.

RHP Matt Shoemaker

2020 age: 33

Key stat: 137.1 innings thrown since 2016

Arm issues have plagued him throughout his career, but this time it was a freak torn ACL on a rundown ending Shoemaker’s season.

Signed for $3.5 million last winter after being non-tendered by the pitching-needy Los Angeles Angels, Shoemaker is still arbitration eligible and under control for the 2020 season, giving the Blue Jays some options as far as contract structure with the veteran righty.

Even though he made just five starts in a Jays uniform this season, Shoemaker, as he’s done throughout his career, flashed enough to be given another chance.

You can still dream there’s another 2016 season — 3.88 ERA and 3.5 fWAR across 160 innings — in that arm.

LHP Ryan Borucki

2020 age: 26

Key stat: 21.2 total innings in 2019

One of the more disappointing developments of the 2019 season is Borucki’s long history of left elbow issues rearing their ugly head once again.

After three healthy seasons rebuilt his project stock and propelled him to his major-league debut last summer, Borucki was shut down early on in spring training and eventually underwent surgery to remove bone spurs Aug. 8.

He’s expected to be full go by spring training, but unlike this year when he was fully expected to be a part of the rotation, next spring he’ll have to prove his health and battle his way back up the depth chart.

RHP Jacob Waguespack

2020 age: 26

Key stat: 2.4 BB/9

A few weeks ago, Atkins, in trying to explain how they’re going to build a postseason-calibre rotation, pointed out a couple of success stories from his time in Cleveland: Corey Kluber and Mike Clevinger.

They’re both great stories, too.

Kluber was a good but not great prospect they acquired in a trade, one that blossomed into a Cy Young winner.

Similarly, Clevinger was a decent arm acquired via trade, and he took off when he joined the Indians organization.

Atkins is adamant they’ll have one of those stories soon. He said it on the record.

Waguespack may not be that guy, but he’s proving to at least be worth more than the two months of Aaron Loup that it took to acquire him.

When given the chance to start without being sheltered by an opener, the big right-hander has run up a 2.97 ERA in seven starts, and he’s doing it with odd reverse platoon splits, dominating lefties and getting hit hard by righties.

His gem Thursday night against a powerful Los Angeles Dodgers team got the attention of the front office.

LHP Thomas Pannone

2020 age: 26

Key stat: 13 home runs allowed in 65.2 innings

Despite multiple holes in the rotation this season, the Jays have been hesitant to give Pannone much run, which is a good indication of how they view him long term.

Homer prone with a 1.8 HR/9 rate this season, Pannone’s bloated 6.44 ERA is pretty.

As a starter, it’s even worse at 10.65, but his 4.07 mark in relief provides hope he can use his curveball to get outs in the bullpen.

RHP Sean Reid-Foley

2020 age: 24

Key stat: 6.0 BB/9

The story with Reid-Foley is pretty straightforward.

The slider is nasty and there’s enough juice on the fastball … when he can throw it for strikes.

Without improved fastball command, Reid-Foley’s future lies in the bullpen, but he could be a very intriguing power setup arm once things are simplified for him.

That future could be coming soon.

RHP Julian Merryweather

2020 age: 28

Key stat: Six innings thrown past two seasons

The Jays front office spent the first half of the season talking up how good Merryweather was looking in bullpen sessions down in Dunedin, before he finally returned to the mound for real in June.

It didn’t last long.

Six rehab innings into his return from the Tommy John surgery he had in March of 2018, Merryweather had to be shut down with what was described as forearm fatigue.

Obviously, not good.

At this point, Merryweather is expected to be recovered in time for spring training, but he’s just a lottery ticket.

RHP Yennsy Diaz

2020 age: 23

Key stat: 12 home runs allowed in 130.1 innings

Thrown into the fire for a spot start against the lowly Baltimore Orioles on Aug. 4, Diaz did not fare well, showing even the worst MLB teams are a huge challenge for a 22-year-old being called up straight from Double-A.

Diaz faced seven batters, got two outs, and quickly hit the showers with four walks and zero strikeouts on his resume.

He’s a fly-ball leaning pitcher, but Diaz always manages to keep the ball in the park, giving up less than one homer per nine innings this year in New Hampshire.

Added to the 40-man roster last winter, Diaz needs some Triple-A seasoning to start 2020, and a full season there might be smart.

RHP Patrick Murphy

2020 age: 25

Key stat: 52 per cent ground-ball rate in Double-A

It’s been an eventful season for Murphy, a third-round pick from the 2013 draft.

The Florida State League pitcher of the year in 2018, Murphy started finding his Double-A groove in the month of May, putting together a run of five starts that saw him post a 1.59 ERA, strike out 39, and walk just four across 34 innings.

That had him in the conversation for a spot start at the big-league level, an idea the Jays front office eventually decided against.

Then it got interesting.

An illegal toe-tap movement forced him to undergo a delivery change, before he was shut down in mid-July with a shoulder issue.

Added to the 40-man last winter, Murphy was expected to join the Blue Jays as a September call-up, but he may not be healthy enough to pitch just yet.

RHP T.J. Zeuch

2020 age: 24

Key stat: 57.5 per cent ground-ball rate

These next three names are not yet on the 40-man roster, but Zeuch and Anthony Kay will have to be protected this winter.

They could be added in short order if the Jays want to get a look in September.

Zeuch, otherwise known as King Sink, a moniker handed to him by Pearson, is exactly that: A worm-burning righty who doesn’t strike many batters out, as evidenced by his 4.6 K/9 in 11 Triple-A starts.

The no-hitter this week against Rochester featured just three Ks.

It may not be the sexiest profile, but Zeuch is a low-upside back-end starter capable of eating some innings, something the Jays could use.

LHP Anthony Kay

2020 age: 25

Key stat: 10.4 K/9 in five starts with Triple-A Buffalo

After struggling with a 6.61 ERA in seven Triple-A starts in the New York Mets’ organization, Kay has found more success with the Jays, posting a 2.36 ERA in five starts and striking out more batters in the process.

He’s also walked too many — 5.7 BB/9 — but he’s gotten better with each and every start.

The ultimate upside is currently in question, but the 2016 first-rounder has a solid three-pitch mix and could be an arm that eventually puts up better results than the scouting reports suggest.

He’s one of the better bets to crack the opening day rotation with a strong spring.

RHP Nate Pearson

2020 age: 23

Key stat: 1.99 ERA across three levels

Stuff, results, and health.

Pearson has put it all together in 2019 and he’s now one of the best three or four pitching prospects in the game.

This year, the goal was to slowly build up his innings, and he currently sits at 90.2 with a couple starts left in his season.

Previously, the most he had thrown in his three professional seasons was 20, and the Jays player development department kept him on a strict five-inning/two-inning plan in the first half of the season, before loosening the reins in the second half.

Finally allowed to pitch deeper into games, the massive right-hander with the 103-mph fastball has gone five-plus innings in each of his last six starts, including seven scoreless in his Triple-A debut.

He doesn’t have to be added to the 40-man roster until the winter of 2020, so the roster shuffle will factor into when he finally arrives in the majors.

It’s unlikely he breaks camp with the Jays next spring, and they’ll likely find a way to limit his innings early on, but expect to see Pearson in Toronto next summer if everything goes according to plan.