If the right-hander's first two starts of the season are any indication, the struggling Pirates offense could have a hard time snapping out of its funk Friday night.
Looking to open 3-0 for the second time in three seasons, Arroyo takes the mound for the Cincinnati Reds as they return home to open a four-game set with Pittsburgh.
Cincinnati averaged 4.8 runs on the road but has scored 7.5 per game at home, where it has outscored Pittsburgh 73-40 while winning 12 of 15.
Arroyo (2-0, 2.08 ERA), who started the 2009 season 3-0, has also excelled in the series, going 5-1 with a 1.73 ERA in his last six meetings with the Pirates. That includes a 0.66 ERA during wins in his last two home starts against them.
Despite battling an ongoing case of mononucleosis, Arroyo recorded his fifth straight win dating to last season after limiting Arizona to eight hits and one unearned run over six innings of Saturday's 6-1 victory.
The Pirates (5-7), meanwhile, can't seem to get anything going offensively, and saw their batting average drop to .223 after collecting just four hits for the second consecutive night Thursday.
Manager Clint Hurdle's team has dropped four straight while averaging 2.5 runs.
Charlie Morton (1-0, 2.08), the Pirates' scheduled starter, allowed five hits and three runs - two earned - in seven innings of Saturday's 6-4 loss to Colorado but didn't factor in the decision.
Morton, who has walked five batters in each of his two starts, is 0-4 with a 7.18 ERA in his last five starts against the Reds.
Cuban left-hander Aroldis Chapman will get a few days of the rest.
Chapman, the 23-year-old, was pulled after two batters in his appearance Wednesday in San Diego when he showed a lack of velocity -- well, a relative lack, as he hit 94 mph twice.
But Chapman had been consistently over 100 and hit 103 in earlier appearances.
Dr. Tim Kremchek, the Reds' medical director, was with the team and examined Chapman afterward.
"There's no concern," general manager Walt Jocketty said. "He has some (elbow) inflammation, which is not unusual for someone who pitches a lot and throws as hard as he does.
"They put him on an anti-inflammatory. We'll give him a day or two off."
Chapman's outing Wednesday was his fourth in five days. The Reds are still trying to figure out how much they can use Chapman.
"This is what we've been trying to figure out and find out," manager Dusty Baker said. "How much can he pitch? A lot of people want him to be the closer, but you've got to be able to pitch consecutive days, sometimes two or three days in a row."
The Reds converted Chapman from starter to reliever last year. They obviously think he's up to the role.
"We think he's capable of pitching a lot," Jocketty said. "We'll keep an eye on it."
--2B Brandon Phillips expects to be in the lineup Friday after tweaking his groin making a throw Wednesday. "He's fine," Reds' general manager Walt Jocketty said. "(But) Dusty (Baker) might decide to give him another day."
--OF Fred Lewis (oblique) began a rehab assignment with Class AA Carolina, going 1-for-3 Thursday. "He didn't have a lot of playing time when he got hurt," Reds GM Walt Jocketty said. "He needs to get at-bats to gets his timing. It will be at least a couple of weeks."
--RHP Jose Arredondo, who had Tommy John surgery in February 2010, has pitched two scoreless innings in his first two rehab appearances for Class AA Carolina. The Reds plan to keep him on rehab for the full 30 days.
--INF Miguel Cairo has not started a game. Friday's series opener against the Pirates could be his first, with 2B Brandon Phillips (groin) hurting.
--LF Jonny Gomes walked again Wednesday and has 14 walks this season. He didn't record his 14th walk last year until June. Gomes' on-base percentage is .479.
BY THE NUMBERS: 27th -- Where the Reds will select in the first round of the draft, their lowest first round pick ever.
QUOTE TO NOTE: "This is what we've been trying to figure out and find out. How much can he pitch? A lot of people want him to be the closer, but you've got to be able to pitch consecutive days, sometimes two or three days in a row." -- Manager Dusty Baker, on LHP Aroldis Chapman.
--LHP Aroldis Chapman (left elbow inflammation) was shut down for a few days as of April 14. The ailment wasn't considered serious.
--RHP Homer Bailey (sore right shoulder) went on the 15-day disabled list retroactive to March 24. He threw a bullpen session April 8, and he pitched a simulated game in extended spring training April 12. He is scheduled to make a rehab start for Class AAA Louisville on April 17.
--RHP Johnny Cueto (right shoulder impingement) had to leave his March 11 start after two innings, then had to leave after one inning March 19. He went on the 15-day disabled list retroactive to March 22. He threw two innings in extended spring training April 11. He is scheduled to make a rehab start for Class AAA Louisville on April 16.
--RHP Jared Burton (right shoulder inflammation) went on the 15-day disabled list retroactive to March 29. He suffered a setback in early April and was shut down from throwing.
--OF Fred Lewis (strained right side) went on the 15-day disabled list retroactive to March 27. He began a rehab assignment with Class AA Carolina on April 14, and he is expected to spend at least a few weeks in the minors.
--RHP Jose Arredondo (Tommy John surgery in February 2010) went on the 15-day disabled list retroactive to March 25. He began a rehab assignment with Class AA Carolina on April 11, and he is expected to stay the full 30 days.