The Royals won the first game 5-1 on Monday to extend their season-high winning streak to six games. The Indians have lost three in a row.
The 37-year-old left-hander has pitched for eight major league teams in his 16-year career, and since joining the Indians, he has been one of the top relievers in the American League.
In 40 appearances with the Indians, Perez has a 1.08 ERA while averaging 10.8 strikeouts per nine innings and holding opposing batters to a .120 batting average.
Perez's 1.08 ERA is the second lowest among AL relievers, and it's the lowest ever by an Indians reliever with a minimum of 40 appearances.
"He's been terrific," Indians manager Terry Francona said. "He's held his stuff so well. We've allowed him to face right-handed hitters, and he's been great. It doesn't matter what inning we bring him in. We use him when it makes the most sense. When he's in the game, there's a lot of importance going on."
Tuesday's pitching matchup features Royals left-hander Danny Duffy and Indians right-hander Mike Clevinger. Based on Duffy's history with Cleveland, the Indians are one of his least favorite opponents.
In 18 career appearances (14 starts) against Cleveland, Duffy is 2-9 with a 5.38 ERA. The only team that has hung more losses on Duffy than Cleveland is Detroit (10).
In three starts against the Indians this year, Duffy is 0-3 with a 10.80 ERA. His last start against Cleveland came July 3, a 6-4 loss in which he pitched six innings, giving up six runs and eight hits with three strikeouts and two walks.
Duffy won his last start, a 9-2 decision over the Tigers on Aug. 29. In that game, he pitched six innings, allowing one run and two hits with six strikeouts and three walks. In four starts in August, Duffy was 1-2 with a 6.04 ERA.
Clevinger is an unsung member of a Cleveland starting rotation whose 3.40 ERA ranks second in the AL, trailing only Houston (3.20).
Clevinger ranks seventh in the league in innings pitched (170 1/3) and eighth in ERA. He hasn't lost since July 28. In six starts since then, he is 3-0 with a 2.21 ERA.
Clevinger's last start was a 5-3 win over Minnesota on Aug. 30, when he pitched 6 2/3 innings, giving up no earned runs and four hits with nine strikeouts and one walk.
The last time Clevinger faced the Royals was Aug. 24, a 5-4 Indians loss, which was not charged to Clevinger. In that game, he pitched six innings, allowing three runs and four hits, with eight strikeouts and two walks.
In eight career appearances (seven starts) against Kansas City, Clevinger is 4-0 with a 2.49 ERA.
The Indians on Monday placed third baseman Josh Donaldson on the 10-day disabled list with a strained left calf. Donaldson was acquired in a trade with Toronto on Aug. 31.