In his past nine starts, Bello has a 2.60 ERA. The 24-year-old has allowed no more than two earned runs in eight of those outings.
Bello (4-4, 3.49 ERA) has pitched at least seven innings in three of his past five starts.
"He keeps getting better," Red Sox manager Alex Cora said. "His (pitch) usage is getting where we want it to. He's been able to develop his slider while in the big leagues. His changeup has always been a weapon, and he's using his fastball in different areas.
Bello, who dealt with forearm tightness in spring training, was especially impressive in his past two starts, both of which were against the New York Yankees. He struck out a career-high eight batters in seven innings during Boston's 4-1 triumph over New York on Sunday. He held the Yankees to one run on four hits and three walks.
In his previous outing, Bello allowed two runs on three hits in seven innings to help the Red Sox post a 3-2 victory over New York. He fanned three and walked two
"He's a kid who came into the league last year with all the hype in the world and struggled for a little bit, but it seemed like he got better with every start," Red Sox utility man Enrique Hernandez said. "This year he didn't really get a spring training and had to basically go through spring training in the regular season. The first couple outings weren't what he wanted
"This year it's the same story as last year -- every time he takes the mound, it seems like he gets better."
Bello has never faced the White Sox, who have lost eight of their past 11 games
White Sox catcher Yasmani Grandal was scratched from the team's 6-3 loss to the visiting Texas Rangers on Wednesday due to a right knee injury and is listed as day-to-day
Chicago also was without Tim Anderson on Wednesday. The shortstop was not in the starting lineup for the fourth straight game because of a right shoulder injury.
One positive for Chicago on Wednesday was the effort by reliever Touki Toussaint, who tossed four hitless innings during his White Sox debut. Toussaint, 27, was designated for assignment by Cleveland on Saturday and was claimed off waivers by the White Sox on Tuesday
"It's been a whirlwind this last week," Toussaint said following the Wednesday game. "They told me to be ready to pitch."
Right-hander Lucas Giolito (5-4, 3.54 ERA) is Chicago's scheduled starting pitcher for Friday. Giolito, one of several White Sox players who has been mentioned in trade rumors, has made five career starts against the Red Sox, going 1-1 with a 5.63 ERA and 29 strikeouts in 24 innings
The Red Sox will try to end a two-game losing streak and will be without outfielder Alex Verdugo, who was placed on the bereavement list on Thursday. Verdugo is batting .303 with five home runs and 31 RBIs in 71 games this season and has hit safely in past 12 games
The Red Sox also will be without backup catcher Reese McGuire, who was placed on the 10-day injured list due to an oblique strain. McGuire has a .267 average with 11 RBIs in 40 games this year
--Field Level Media