GOODYEAR, Ariz. -- Reynaldo López’s fastball entered the high-90 mph range in his first full season in the White Sox bullpen a year ago. After a short adjustment period, the results followed.

López pitched to a 1.87 ERA over his final 42 appearances last season, with 47 strikeouts and only five walks in 43 1/3 innings. Opponents batted .188 against him in that span with one home run.

“It was more mental than anything,” López said of the relief role. “Be ready every day instead of once every five days. It took awhile to get used to. The first two months were not good, but after that, everything was clicking.”

López’s power arm is a major component in a White Sox bullpen featuring right-hander Kendall Graveman and left-handers Aaron Bummer and Jake Diekman. The crew will be further strengthened when Liam Hendriks and Garrett Crochet are cleared to return.

Bullpen roles have not been defined, but manager Pedro Grifol has indicated that usage will be determined by game situations, not a particular inning designation.

“He’s a special talent, and he's also a special kid,” said Grifol, who strategized against López as the Royals’ bench coach from 2020-22. “He likes the moment. He likes the stage. He’s a good athlete. Fields his position well. Great feet.

“I’ve been watching him pitch for awhile now. I think he is special. That is what I thought from the other side. There is really not much to not like. I am looking forward to watching him pitch all year long.”

Like a lot of high-leverage specialists, López said his adrenaline rises in those situations.

“[Grifol] knows that I am not scared,” said López, who was 6-4 with a 2.76 ERA in a career-high 61 games in 2022. “I can throw every pitch in every count. As a starter, it is not the same.”

Colas starts in center
Non-roster invitee Oscar Colas made his first start in center field on Thursday after spending most of the spring in right, and the White Sox surely liked what they saw.

Colas, 24, made a diving catch on Miles Straw’s sinking line drive to short center with a runner on second base for the second out of the sixth inning. Colas threw the ball back to the infield from a sitting position.

White Sox system evaluators believe Colas can play in center field after playing 70 games there at three Minor League levels in 2022 in his first season in the U.S. following four seasons in Japan. He also played 34 games in right.

“We have to be prepared,” Grifol said. “If we make decisions based on whether we might need him to play center field on occasion, we all have to be comfortable with it.”

Giolito, Bummer ramping up
Lucas Giolito threw four shutout innings in a “B” game against the Los Angeles Dodgers on Thursday, a day after his scheduled start against San Francisco was rained out. Giolito gave up three hits, struck out six and did not walk a batter on 63 pitches.

Grifol said the one-day delay will have no impact on Giolito's preparation for the regular season. Giolito has been the Sox’s Opening Day starter the last three seasons, an honor awarded to Dylan Cease this year.

Bummer threw a 30-pitch bullpen session, his third of the spring, on Wednesday, and is scheduled to throw live batting practice this weekend as he works his way back from lat soreness. He believes he is on track to open the regular season with the team.