It's no coincidence that Jake Arrieta's rapid growth as a big league pitcher since he joined the Chicago Cubs midway through the 2013 season mirrors the growth of his facial hair. The man with the lumberjack-esque beard barely resembles the clean-cut prospect who came out of TCU, in more ways than one.

Just weeks after leaving the Baltimore Orioles with little more than stubble in 2013, Jake Arrieta began his ascent to ace status in Chicago sporting a full beard.

"It's definitely top-of-the-line," said Jason Hammel, who has pitched with Arrieta in both Baltimore and Chicago. "I don't think he ever had a beard when we were over there [Baltimore]."

"When he did make that turn [into an elite pitcher], the beard showed up. Maybe it's a superstition at this point. I don't know, but I definitely associate the beard with Jake now. That's his image."

Here's how Arrieta's facial hair and pitching acumen have progressed over the years:

2006: Clean-cut college kid

Beard status: A young Arrieta, who pitched two seasons at TCU after a stint at Weatherford College, was a clean-shaven student during his time as a Horned Frog.

Mound status: In Fort Worth, Arrieta was one of the top pitchers in college baseball, going 14-4 with a 2.35 ERA in 2006 and coming back with a 9-3 mark and 3.01 ERA in 2007.

AP Photo/Jerry Laizure

2007: Arizona Fall League

Beard status: After the Orioles selected him in the fifth round of the MLB draft in June, Arrieta made his professional debut under the sun in the Arizona Fall League. The desert heat may have forced the right-hander to compromise, as he grew his hair shaggy but kept his face mostly bare during his time with the Phoenix Desert Dogs.

Mound status: A breakout star in the competitive Arizona Fall League, Arrieta threw 16 scoreless innings with a sub-1.00 WHIP and helped the Desert Dogs win the AFL championship.

Joy R. Absalon/USA TODAY Sports

2008: An Olympian

Beard status: While representing the U.S. at the 2008 Summer Olympics in Beijing, Arrieta sported the first iteration of what would become his trademark beard. The beard had a similar shape to the one he currently sports but was both thinner and cleaner, with sharper edges.

Mound status: Arrieta made one start in Beijing, beating China by throwing six scoreless innings.

Clive Rose/Getty Images

2009: First spring training

Beard status: After he jettisoned the beard late in 2008, Arrieta arrived at spring training with the Orioles with a close-cropped haircut, which he sported on top of a bit of stubble.

Mound status: It was a quiet spring for Arrieta on the mound, as he made just one one-inning appearance for the Orioles.

Mitch Stringer/Icon SMI

2010: The rookie

Beard status: There's a tradition of playful rookie hazing in baseball, and let's hope that was the driving force behind the mustache Arrieta sported for a time during his first campaign.

Mound status: Arrieta started 18 major league games after beginning the season in Triple-A, going 6-6 with a 4.66 ERA.

Mitch Stringer/Icon Sportswire

2011: First full season

Beard status: Arrieta began experimenting a bit in his first full big league season. He eventually settled on that long mop he debuted in 2008 (with thicker sideburns) and a light goatee.

Mound status: After pitching well enough in 2010 to earn a rotation spot going into 2011, Arrieta began to struggle as his ERA increased to 5.05 in his first full season.

AP Photo

2012: From Opening Day starter to the minors

Beard status: Arrieta struggled in his second full season in the bigs while reverting to a shorter haircut and light stubble.

Mound status: Arrieta was tabbed as Baltimore's Opening Day starter in 2012, but a 6.20 ERA in 24 major league starts forced the Orioles to send Arrieta back down to Triple-A.

Kim Klement/USA TODAY Sports

First half of 2013: The final days in Baltimore

Beard status: Arrieta basically carried his 2012 style into 2013, allowing his hair to grow a bit longer and his stubble a bit thicker. Little did we know that a radical change was in the works.

Mound status: The start of the 2013 season was Arrieta's lowest point as a pitcher. In five starts, his ERA ballooned to 7.23 as his command and control issues persisted.

Joy R. Absalon/USA TODAY Sports

Second half of 2013: The turnaround

Beard status: Between his last start for the Orioles in mid-June and his first start for the Cubs in late July, Arrieta became almost unrecognizable. With the team change, Arrieta let his hair down, literally. His beard became much thicker and more defined, while his hair approached its longest length.

Mound status: The Cubs took a flier on Arrieta, and it immediately paid dividends. Over the final few months of the 2013 season, Arrieta improved his ERA by more than three runs while going 4-2 down the stretch.

Brian D. Kersey/Getty Images

2014: Settling in

Beard status: Arrieta carried his late-2013 form into 2014, with a few important grooming adjustments. He cut his hair, and his beard became thicker and fuller in each start without losing its shape.

Mound status: The right-hander continued his strong pitching in 2014, having a career year up to that point, going 10-5 with a 2.53 ERA.

AP Photo/Alex Brandon

2015 regular season: Perfecting his craft

Beard status: The only changes from 2014 for Arrieta's beard were minor, as it became sharper and more angular.

Mound status: Arrieta dominated baseball in 2015, earning the NL Cy Young Award after a no-hitter and a 22-win season. His 1.77 ERA was the second-best mark in baseball.

Mike Zarrilli/Getty Images

2015 playoffs: An impressive run

Beard status: As the Cubs made their first NLCS since 2003, Arrieta allowed his beard to flourish during his team's playoff run. With each passing day, it grew outward, becoming a phenomenon unto itself.

Mound status: Although he was not as dominant in the postseason as he was in the 2015 regular season, Arrieta was superb. He struck out almost 13 batters per nine innings in his three starts.

Joe Sargent/MLB Photos/Getty Images

2016: Arrieta's new normal

Beard status: So far in 2016, Arrieta has carried his impressive 2015 form into the current season. Although it's only the regular season, he has maintained a playoff-level thickness to his beard, along with a maintenance job rivaling that of the outfield at the Friendly Confines.

Mound status: In 2016, Arrieta is already on pace to best his 2015 season. In 15 starts, his 1.74 ERA again ranks second in the bigs, and he also tossed his second career no-hitter.