Brett Anderson, Eddie Butler, Casey Kelly and Alec Mills may not be big names, but with a spring training of tutelage under pitching coach Chris Bosio, they could wind up having a big impact for the reigning World Series champions.

MESA, Ariz.—The Cubs’ defense of their world championship begins in a laboratory here. Though it includes plenty of math and physics, there are no beakers, test tubes, microscopes or white smocks. What you will find are adjoining 10-inch mounds of clay and dirt that slope one foot for every inch. Welcome to the lab of Cubs pitching coach Chris Bosio, where on these bullpen mounds at the team’s training complex, the failed and the anonymous begin to be transformed.

"I know I’m listening to him," said one of his latest lab students, Alec Mills, a 25-year-old righthander who was traded to Chicago by the Royals earlier this month. "He’s had a little bit of success, wouldn’t you say? We already did some special drills this morning."

Including the postseason, the Cubs rolled up 114 wins last year, 113 of which were credited to pitchers they acquired from other organizations. Team president Theo Epstein and general manager Jed Hoyer have keen eyes for finding pitchers on the cusp of breaking out. Often the key to realizing that leap forward happens in Bosio’s lab.

The lab may well be the key to Chicago's chances of repeating as champions. For all the acclaim given to All-Stars such as Jake Arrieta, Kris Bryant, Jon Lester, Anthony Rizzo and Addison Russell, the season might swing on pitchers who walk the grounds here without even the most fervent fans recognizing them: Mills, Brett Anderson, Eddie Butler and Casey Kelly. Combined 2016 production of the four anonymous starters: 3–10 and 13 starts.

The Cubs got lucky last year. I’m not talking about the Giants’ bullpen imploding three outs away from getting the NLDS to ace Johnny Cueto, or injuries to Indians starters Danny Salazar and Carlos Carrasco that forced Cleveland to become only the second team in a quarter century to use starters on short rest four times in the World Series, or—good heavens—17 blissful minutes of a restorative rain delay on the edge of blowing Game 7. Chicago had freakishly good health when it came to its veteran starting pitching.

Four pitchers in their 30s made at least 29 starts last year for the Cubs (Arrieta, Lester, John Lackey and Jason Hammel). It marked only the 11th time so many starters so old worked so often, and the first time in the 12 seasons with penalties for PEDs. Overall, Chicago used 30-something pitchers to start 122 games—also the most since 2005.

What are the odds such luck happens again? Hammel is gone, after Chicago allowed him to pursue free agency and an eventual job with Kansas City. Lester (now 33), Arrieta (who turns 31 next month) and Lackey (38) started 92 regular-season games for Chicago last year. The team played .663 baseball when they started (61–31) and .609 baseball when they didn’t (42–27).

Keeping Lester, Arrieta and Lackey healthy and rested is a priority for the Cubs. The plan to do so includes slow-playing them in spring training—none will work in the first handful of spring training games—and occasionally using a six-man rotation during rigorous portions of the schedule.

Mike Montgomery, 27, figures to replace Hammel in the rotation. (He has never thrown 160 innings in any of his nine pro seasons.) A 2016 graduate of the lab, Montgomery typifies how Chicago finds and improves pitchers. Epstein saw the stuff of a potential 15-game winner buried in middle relief for Seattle. Bosio worked on improving Montgomery's confidence and how he uses his stuff, using Pitch FX data to double the lefthander's curveball usage and dial back his cutter use against righthanders. Montgomery wound up getting the last out of the World Series.

No organization has been better than the Cubs at acquiring and improving pitchers. The list of the lost-and-found in recent years includes Arrieta, Trevor Cahill, Justin Grimm, Kyle Hendricks, Hector Rondon and Pedro Strop. It’s a credit not only to Epstein, Hoyer and Bosio, but also to catching coach and game-planning guru Mike Borzello and run prevention coordinator Tommy Hottovy, the latter of whom synthesizes analytical and scouting information.

This year Chicago will need rotation depth. (Lester and Arrieta combined for 72 starts and 458 innings last year, playoffs included, so beware fatigue.) Here are the four students in Bosio’s lab who are most likely to be the next success story for the Cubs (presented in alphabetical order). And who knows? Maybe one of them might be the next one to get the last out of the World Series.

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Brett Anderson

The big-bodied lefthander once looked like an ace in the making. In 2009, he set the Oakland franchise rookie record for strikeouts in a season with 150. At ages 21 and 22, in his first two seasons, Anderson went 18–17 with a 3.57 ERA in 49 starts. Alas, in six years since then, he has made only 66 starts and averaged only 66 innings per year. The guy simply can’t stay healthy. He has been sidelined because of Tommy John surgery (2011), an oblique strain ('12), a stress fracture in his right foot ('13), a broken index finger and surgery to repair a herniated disk ('14) and another surgery on the same disk ('16). The next back surgery, he said, would end his career.

Epstein signed Anderson for $3.5 million, with incentives that could earn him another $6.5 million. When healthy, Anderson’s package of pitches—low-to-mid 90s sinker, slider, curve and change—is still impressive.

The first thing Bosio noticed about Anderson was that he was landing on the side of his right foot—probably a bad habit caused over the years by compensating for his broken foot and bad back. The flaw would put Anderson in a compromised position at release. His fingers stayed behind the baseball, causing him to "push" the ball toward the plate. Bosio immediately worked with Anderson on getting back to landing in the preferred manner: softly on the ball of his front foot. That change immediately allowed Anderson to get his fingers on top of the ball just prior to release, generating more life and spin on his pitches.

Moreover, as he did with Mills, Bosio made sure he put Anderson in the best possible training group of pitchers this spring: the one with Lester, another big-bodied lefthander.

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Eddie Butler

This is a familiar story about why pitchers don’t develop in Colorado. The Rockies picked Butler in the first round of the 2012 draft (No. 46 overall) out of Radford University. They immediately changed him from a sinkerball pitcher to a four-seam pitcher. The next year they raised his release point five inches. They stressed the importance of pitching repeatedly to the low-and-outside area as a way of combating the effect of altitude on fly balls. Altitude also sapped the bite on his slider and curve.

"Consistency was the biggest problem," he said. "The ball moves three inches at home and six inches on the road, so you find yourself constantly adjusting to what your ball is doing. It’s hard to be consistent."

Butler posted a 7.92 ERA at Coors Field and a 5.40 ERA elsewhere. Last month, the Rockies designated him for assignment, taking away the roster spot of a 25-year-old former first-round pick to make room for Greg Holland, a 31-year-old reliever who did not pitch last season because of Tommy John surgery. Epstein quickly snapped him up in a trade.

The first thing Bosio did with Butler was to tell him he wanted him be himself—to be comfortable pitching in the style that had made him a first-round pick. That meant returning him to a lower release point and to having him use his sinker, not his four-seamer, as his primary fastball. In Chicago, unlike in Colorado, that also means pounding fastballs inside.

If this story sounds familiar, it is. In 2013, Bosio took a former fifth-round pick who needed a change of scenery because his organization kept changing how he threw and returned him to his more natural way of throwing. That organization was Baltimore, and that pitcher was Arrieta, who went on to win the 2015 NL Cy Young Award. Bosio also turned around Strop, who was acquired in that same deal with the Orioles, after he noticed he pitched from the first base side of the rubber during the 2013 World Baseball Classic; Baltimore had him pitching from the third base side.

"You pay attention," Bosio said. "You work with what’s comfortable for a guy."

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Casey Kelly

"This guy may be the most exciting one of all after all is said and done," Bosio said.

The Red Sox, under Epstein, drafted Kelly in 2008 in the first round, 30th overall. It took $3 million to convince Kelly to pass up a chance to play quarterback at Tennessee and a promise to allow Kelly to pitch and play shortstop. In 2009 at Class A Greenville, Kelly posted a 1.12 ERA in the first half of the season before switching to shortstop, when he hit .222. After the season, he decided to concentrate on pitching.

The next year, Epstein traded Kelly and Rizzo to get first baseman Adrian Gonzalez from San Diego. Kelly’s career never took off. He was sidetracked by Tommy John surgery—which robbed him of two to three miles per hour off his fastball—followed by a conversion to the bullpen and then a trade to the Braves, where he spent most of last year in Triple A. Once ranked by Baseball America as the ninth-best pitching prospect in the game, Kelly is now 27 years old with a career major league record of 2–8 and a 6.39 ERA.

(To show you how fickle prospect rankings can be, especially for pitchers, the eight pitching prospects ranked ahead of Kelly in 2010 were Stephen Strasburg, Brian Matusz, Neftali Feliz, Madison Bumgarner, Martin Perez, Jeremy Hellickson, Aroldis Chapman and Tyler Matzek, with Kyle Drabek ranked just behind Kelly. Half of the top 10 have had Tommy John surgery. Further, 19 of the 33 top-ranked pitching prospects from 2010 have had Tommy John surgery—58%—and only four of them are current major league starters who have not had the surgery: Bumgarner, Hellickson, Shelby Miller and Julio Teheran.)

Epstein, who signed Kelly originally, and Hoyer, who traded for him in San Diego, signed Kelly in January as a minor league free agent.

"The one thing we’d like to do with him is create some deception," Epstein said.

A righthander, Kelly throws from the first-base side of the rubber with a high three-quarters release point and a front side that opens up early. That means he releases the ball close to the middle of the rubber—he creates almost no angle on his pitches—and "shows" the ball early to the hitter. He might be better served pitching from the third-base side of the rubber and staying closed longer.

Moreover, like Butler, Kelly should re-think how he uses his fastballs. Kelly throws four-seamers twice as often as he does two-seamers, but he may want to reverse that rate. That’s because Kelly is a short-strider with low spin rate on his four-seam fastball—a bad combination. His four-seam fastball has below-average velocity (91 mph), but because of his short stride and low spin, the perceived velocity of the pitch (88.9 mph) is even further below average. A short stride, in which a pitcher throws over a firmer front leg, and a low spin rate are actually preferential for a sinkerball pitcher.

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Alec Mills

Mills never was anybody’s idea of a hot prospect. The righthander walked on at Tennessee-Martin, was drafted in the 22nd round in 2012 by Kansas City, blew out his elbow in '13 and throws with average velocity, in the mid-90s. The Royals designated him for assignment after they signed Hammel.

"I got designated at 4 o’clock and traded to the Cubs at 6 o’clock," he said. "Everything happened so fast."

Bosio quickly heard from people he knew in the Kansas City system who told him, "I can’t believe you got him."

The first thing Bosio did with Mills was to ask him a question.

"Did you watch the World Series last year?"

"Sure," said Mills, a Cubs fan growing up.

"Who do you see yourself most like?"

"Kyle Hendricks. I think my stuff is similar. I like to pitch off of changing speeds. But nobody’s ever showed me how."

The next thing Bosio did was to assign Mills to shadow Hendricks in the same pitching group in spring training.

"I’ll be watching and asking questions," Mills said.

The minor league version of Mills actually has been a bit better than the minor league version of Hendricks, whom Epstein stole in a 2013 trade with Texas. In a similar amount of career minor league innings, Mills posted better rates than Hendricks in walks per nine innings (1.9, 2.0), strikeouts per nine (8.6, 7.7) and strikeouts to walks (4.44, 3.76). In 2015, Mills struck out 111 and walked only 14.

Now Bosio is showing Mills how to change speeds effectively. The key: pounding sinkers in, which opens up the outside of the plate and the occasional elevated four-seamer.