PHOENIX -- Jesus Aguilar was no lock to make the Brewers' Opening Day roster last year, but he slugged his way to Miller Park by bashing seven home runs in 25 Cactus League games.
A year earlier, Yadiel Rivera won his spot with a series of clutch ninth-inning hits. Further back, the likes of Casey McGehee and Erick Almonte forced their way into the Opening Day mix with productive springs.
As the Brewers begin Cactus League play on Friday with split-squad games at home against the Cubs and on the road against the Giants, opportunity abounds for the next dark horse to play his way to Milwaukee. Brewers manager Craig Counsell hasn't yet named his starting pitchers for the 2 p.m. CT games, one of which (against the Cubs) will be on MLB.TV.
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Here are a handful of dark horses to watch this spring:
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Taylor Williams
The hard-throwing right-hander missed two full seasons because of Tommy John surgery but returned in 2017 with 57 strikeouts in 46 2/3 innings at Double-A Biloxi, which was followed by a surprise September callup. For the first time in years, he was free of restrictions this winter.
"It was huge confidence boost, I think," Williams said. "That was the biggest thing. I had the little bit of experience being with the team in Spring Training, but actually being up there in Milwaukee with the big league club and playing with the team when we were playing for the playoffs, it was big for me."

He has "no limits" this spring, and while he might be on the fringes of a full bullpen competition, Williams' electric arm is worth keeping an eye on. He turns 27 in July, so there is still plenty of time for a Major League career if he can stay healthy.
Aaron Wilkerson
This may be a stretch of the term "dark horse," since Wilkerson has been mentioned for weeks among the group of starting pitchers vying for a spot in the Opening Day rotation. He is an underdog based on where he stands relative to the other competitors for two open spots, a group that includes veterans like Yovani Gallardo and Wade Miley, others with a bit more experience like Junior Guerra and Brent Suter and a top pitching prospect in Brandon Woodruff.
But Wilkerson is in the mix, and he has a definite chance. He won a September callup last year by going 11-4 with a 3.16 ERA at Double-A Biloxi, and he pitched a seven-inning gem in St. Louis on the final day of the Major League regular season.

Nate Orf
Versatility is key to Orf's outside chances this spring. He played all nine positions in a Class A Advanced game in 2014 and has significant experience at second base, third base and the corner-outfield spots. He's also adept at the plate, with a .385 on-base percentage in five Minor League seasons.
What would it take for Orf to make the cut? Probably an injury to Hernan Perez or Eric Sogard, who are similarly versatile and ahead of him on the depth chart.
Ernesto Frieri
Of the Brewers' non-roster invitees bidding for the bullpen, former Reds and D-backs reliever J.J. Hoover looks to have the best shot. So for a true dark horse, we'll go with Frieri, the former Angels closer who has made only six appearances in the Majors over the past two seasons. He didn't have much success in seven innings with Texas last year, but he was throwing as hard as he did when he saved 37 games for the Angels in 2013. If other pieces fall, Frieri's experience could make him appealing.
"It feels like two years ago I was the rookie," Frieri said. "Now I'm the old guy."