Vargas takes the mound opposite McGowan as the Royals open a three-game home set against the Blue Jays on Tuesday night.
Vargas (2-0, 1.54 ERA) is looking to open 3-0 as a starter for the first time after allowing two earned runs or fewer in each of his first five outings. The left-hander, holding opponents to a .214 average, has walked just eight in 35 innings.
"He doesn't challenge hitters, he makes pitches," manager Ned Yost told MLB's official website. "It gives him the confidence that, 'If I make a little bit of a mistake, somebody's still going to be there to catch it.'"
Vargas yielded three runs - two earned - in six innings in Wednesday's 5-3 loss at Cleveland.
"It's better than doing bad. The idea is to do well. It's pretty self-explanatory," he said. "It really doesn't matter until you pitch the next game you're supposed to pitch. None of it all matters if you don't pitch well the next time out."
McGowan (1-1, 6.88) earned his first win since 2008 with a strong showing in a 2-0 victory at Baltimore on April 11, but he's allowed 13 runs in his other three starts spanning just 10 2-3 innings. The right-hander, who has battled through his fair share of injuries over the years, is averaging just over 79 pitches per outing.
"The body just feels like it runs out of steam a little bit," McGowan said. "I shouldn't be feeling that, I should be at the point where I can go 90-100 (pitches), especially the way my arm feels. It feels great."
McGowan said he started to tire after surrendering six runs in four-plus innings in Wednesday's 10-8 loss to the Orioles. He could be moved to the bullpen if he can't get on track.
"We've always told him that if something is wrong or doesn't feel right, to let us know," manager John Gibbons said. "And he's guaranteed us he would."
The Blue Jays (12-13) dropped four in a row before beating Boston 7-1 on Sunday. Brett Lawrie hit his sixth homer and Melky Cabrera, one of a record six players from the Dominican Republic in the lineup, stayed hot with two hits and an RBI.
"It was a much-needed win, I will definitely say," Gibbons said.
With 39 hits, Cabrera is one away from breaking the team record for March and April. The former Royals outfielder, batting .409 with five extra-base hits during a 10-game hitting streak, is the first Blue Jay to hit safely in 24 of the first 25 games.
Kansas City (12-12) returns home after taking two of three against Baltimore. Omar Infante went deep and matched a career high with six RBIs in Sunday's 9-3 victory.
The Royals are 12-0 when scoring at least four runs compared to 0-12 when they don't.
"I take it we need to score four runs," Yost said. "We're trying to do it more."
Vargas is 1-3 with a 5.67 ERA in six career starts against the Blue Jays but hasn't faced them since 2012. Edwin Encarnacion is 5 for 15 with two homers and two doubles in their matchups.
Toronto took 10 of 14 from the Royals over the previous two seasons, including six of seven in Kansas City.
Royals designated hitter Billy Butler, hitting .209, is 2 for his last 46 against the Blue Jays.