MESA, Ariz. -- The Cubs didn't build off their 2016 World Series championship in large part because they failed to develop pitching. From when former president of baseball operations Theo Epstein and general manager Jed Hoyer arrived in Chicago in October 2011 until the end of their respective tenures, the most successful arm signed and developed by the franchise has been Adbert Alzolay, who has seven wins in 159 1/3 innings in the big leagues.

Now in a rebuilding phase, the Cubs are prioritizing homegrown pitching. One of their highest-ceiling arms is 2019 first-rounder Ryan Jensen, who's working on polishing his game in the Arizona Fall League.

After getting knocked around in his first two outings for the Mesa Solar Sox, Jensen was at his best Wednesday. The Cubs' No. 15 prospect spun four scoreless innings in a 12-0 rout of the Glendale Desert Dogs. He allowed just two hits while fanning five, delivering 33 of 46 pitches for strikes. The Fresno State product relied mostly on his two-seam fastball, which sat at 94-96 mph and touched 98, while mixing in some 88- to 90-mph sliders and 81- to 83-mph curveballs.

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Jensen's best pitch is his heater, which has more velocity than a typical sinker; it finished off four of his five whiffs Wednesday. He can push triple-digits with his four-seam fastball, but he considers it the least effective of his five pitches -- he also has a changeup -- it lacks life and gets hit.

"My two-seam fastball, sinker, has a lot of movement and run to it," Jensen said. "So I can throw it in any count and get a ground ball. I do throw a four-seamer, depending on what count I'm in and who's hitting and how the guy's swinging the bat."

The 23-year-old didn't get much of a chance to develop early in his pro career. He pitched just 12 innings in the Minors after signing for $2 million in 2019, then was limited to working out at home and a trip to the instructional league when the COVID-19 pandemic wiped out the '20 Minor League season.

Jensen struggled during May and June this year before adapting and posting a 2.23 ERA with 52 strikeouts (with just 15 walks) to go along with a .174 opponents' batting average across his final 11 starts (48 1/3 innings) between High-A and Double-A.

Jensen knows he still has more refinements to make to his secondary pitches and his command before he's ready for Wrigley Field. But he's pleased with the progress he has made thus far.

"I have more pitchability than I did in college," said Jensen, who sports a 7.56 ERA with 12 strikeouts in 8 1/3 Fall League innings. "I was mainly a fastball/slider guy, and my slider wasn't very good. Just getting into pro ball, mixing my pitches more, facing better hitters -- because you can't just throw fastball to these guys -- has helped.

"In college, my control was a little sporadic. I definitely have more feel for the zone now."

Jensen's outing and a 15-hit attack enabled Mesa to improve to 7-5 and hold onto first place in the AFL's East Division. Marlins left fielder JJ Bleday (376 feet with an exit velocity of 104 mph) and Cubs right fielder Nelson Velazquez (377 feet at 107 mph) hit back-to-back homers off White Sox right-hander McKinley Moore to blow the game open during a six-run fourth inning.

Bleday, Miami's No. 5 prospect, and third baseman Logan Davidson, Oakland's No. 12 prospect, each had three hits for the Solar Sox, while fellow Cubs righty Caleb Kilian followed Jensen with three shutout innings, striking out six and topping out at 97 mph.

Glendale dropped to 7-5, two games back in the West Division. Dodgers DH Carson Taylor collected two of the Desert Dogs' five hits.