Around the Horn: Herrera gives Sox a proven arm in the bullpen

Joakim Soria, Xavier Cedeno, Luis Avilan.

David Robertson, Tommy Kahnle, Anthony Swarzak, Dan Jennings, Tyler Clippard.

They were all productive relief pitchers for the White Sox, and they were all traded for prospects during the last two seasons.

When it comes to evaluating managers, bullpen usage is a key criterion. That's why it's still hard to get a read on Rick Renteria.

Rather than make excuses, Renteria has tried to make the most of calling on unproven relievers instead of battle-tested veterans.

"It's given them a chance to respond and show us what they're capable of doing in particular situations," Renteria said.

Young relief pitchers like Jace Fry and Ian Hamilton have responded pretty well and might stake claims in the Sox's bullpen of the future.

Others, like Aaron Bummer, Ryan Burr, Jose Ruiz and Caleb Frare, are trying to prove they belong.

The Sox's bullpen is still a work in progress, but the unit should be better this year thanks to the addition of two established arms.

Alex Colome, acquired from the Mariners in a trade for catcher Omar Narvaez, enters the season as the White Sox's likely closer.

Kelvin Herrera should be his primary setup man.

Signed to a two-year, $18 million contract on Jan. 8 - the deal also includes a $10 million club option for 2021 - Herrera has a 2.82 ERA, 113 holds, 60 saves and 454 strikeouts in 460 innings over eight seasons with the Royals and Nationals.

Traded from the Royals to Nationals last June, Herrera was limited to 10 games after the all-star break due to a Lisfranc fracture in his left foot.

The 29-year-old started spring training slowly, but Herrera has looked good over 6 Cactus League appearances (3.18 ERA, 5 strikeouts in 5⅔ innings) and should be ready to go when the season opens next Thursday at Kansas City.

"He's a proven high performer in the American League," White Sox general manager Rick Hahn said. "We think he will give Ricky another dynamic late-inning option to help shorten up some games and allow us to develop some of our younger relievers on their natural path. We foresee no long-term implications from the foot surgery."

Nate Jones is another veteran in the Sox's bullpen, but he has a long injury history and has not been sharp (15.34 ERA) in spring training.