CLEVELAND -- The Cleveland Indians' offense continues to be wildly erratic, but their starting rotation, which has been plagued by some nagging injuries, is starting to get on a roll.

On Sunday at Progressive Field, the ace of the staff, Corey Kluber, will take the mound as the Indians attempt to complete a three-game sweep of the Toronto Blue Jays.

In their last 12 games at Progressive Field, Indians starting pitchers have a 1.92 ERA.

All you need to know about the up-and-down nature of the Cleveland offense is the scores of the Indians' wins in the first two games of this series: 13-3 and 2-1.

The Blue Jays, meanwhile, will try to bounce back from still another walk-off loss suffered Saturday night. Toronto leads the American League with eight walk-off losses.

"They're all tough," Blue Jays manager John Gibbons said Saturday night after Francisco Lindor's walkoff home run in the 10th inning.

"We've just got to keep battling. We'll show up tomorrow."

The pitching matchup Sunday afternoon will be Kluber (7-3, 2.86 ERA) vs. Toronto left-hander J.A. Happ (3-6, 3.55).

Kluber will be pitching on two extra days of rest as the Indians pushed his start back a few days while he was dealing with a stiff neck. Kluber spent most of May on the disabled list with a lower back strain, but since being activated he has been one of the best pitchers in the majors.

In nine starts since coming off the DL, Kluber is 4-1 with a 1.56 ERA while holding opposing teams to a .160 batting average. In those nine starts, Kluber is averaging 13.4 strikeouts per nine innings (94 strikeouts in 63 1/3 innings) .

Kluber ranks fifth in the American League in strikeouts, which is remarkable in that the four pitchers ahead of him all have between four and six more starts than Kluber does.

Toronto, however, has historically given Kluber trouble. He has not faced the Blue Jays this year, but in five career starts against them, Kluber is 1-3 with a 5.34 ERA. That's Kluber's highest ERA versus any major league opponent against whom he has made at least three starts.

The Blue Jays' hitters who have had the most success against Kluber are Josh Donaldson, who has a career average of .375 (6-for-16), Ryan Goins (3-for-6) and Jose Bautista (3-for-9).

Cleveland's starting rotation is currently in a state of flux. With the addition of Danny Salazar, who came off the disabled list and started Saturday night, the Indians are currently using six starters: Kluber, Salazar, Carlos Carrasco, Trevor Bauer, Mike Clevinger and Josh Tomlin. However, manager Terry Francona said he has no intention of employing a six-man rotation.

"We're going to go one time through the rotation with six, but I can't see us doing it forever," Francona said. "If you go with a six-man rotation, there's no room for a hiccup from any of them, because then you'd get into your bullpen too much."

Like Kluber, Happ has been pitching well of late. In his last seven starts, Happ is 3-2 with a 2.43 ERA. He has not faced the Indians this season, but in six career appearances against Cleveland he is 3-1 with a 2.86 ERA.