Vargas worked two scoreless innings, giving up only a single to Tommy Medica. Vargas was signed as a free agent from the Angels, filling the rotation void left by Ervin Santana.
Vargas got help from left fielder Alex Gordon, who raced in to grab Everth Cabrera's game-opening line drive. Cabrera was in the Padres' lineup for the first time; he missed the first two games with flu.
"I felt fine, was able to throw all my pitches, was able to get acclimated to Salvy (catcher Salvador Perez) back there and we just kind of moved along," Vargas said.
Right-hander Ian Kennedy, obtained by the Padres at the Trade Deadline last year, also reeled off two scoreless innings in his first start. He gave up a double to Mike Moustakas, and a walk with two strikeouts.
Brad Penny, a veteran right-hander who didn't play last year, was touched for five hits and three runs in his two innings for the Royals, but got credit for the victory. Maybin cracked his homer off him in the third inning. It was Maybin's first home since last June 9 when his season ended because of injuries.
"Man, it felt good. I know it's only two games in, but it felt really good to kind of click one," Maybin said. "Just to kind of get that reassurance that the body feels well. You always gain confidence when you're able to put together a good at-bat."
Kennedy appreciated the blast.
"That was nice, I joked and said, 'He's back,'" Kennedy said. "That was a great swing, though. That was like the Cameron Maybin that I've seen hit some far balls against the D-backs, when I was with them."
The Royals scored four runs off right-hander Keyvius Sampson in the third on Gordon's two-run double and RBI singles by Eric Hosmer and Brett Hayes. They added three runs against righty Adys Portillo in the fourth, an inning launched by Justin Maxwell's double.
Royals closer Greg Holland pitched a scoreless inning, giving up only Medico's third straight single. Kelvin Herrera worked a perfect inning with two strikeouts.
Padres reliever Dale Thayer reeled off a perfect seventh with two strikeouts.
Up next:The Royals get their first look at the Cubs' new Spring Training stadium at Mesa, Ariz., at 2:05 p.m. Sunday. Two candidates for the fifth starting spot, Wade Davis and Yordano Ventura, are scheduled to be the first two pitchers for the Royals followed by John Lamb, Francisley Bueno and P.J. Walters. Several regulars are not on the travel roster to Cubs Park, including Billy Butler, Salvador Perez, Alex Gordon, Omar Infante and Alcides Escobar. The Cubs' probable starter is Jason Hammel, a right-hander who was 7-8, including a loss to the Royals, last year for the Orioles. Listen on Gameday Audio.