The Royals could not beat them Tuesday, falling 2-1 in 11 innings, with Joe Panik's single to center proving to be the game-winner.
The Royals left the bases loaded in the eighth, two on in the ninth and had two on when Eric Hosmer grounded into a double play in the 10th. Wotus also said Posey would likely return to catching on Friday after coming off the concussion list and spending two games as the DH.
In that stretch, Posey has won the 2012 MVP Award, three Silver Sluggers and one Gold Glove.
Whit Merrifield, in his first game of the season, homered in the fourth inning. Cain walked the next batter, but set down the next seven to leave after seven innings with the game knotted at 1.
Bumgarner allowed one run, seven hits and a walk while striking out four but was done in by another poor night by San Francisco's offense.
Royals starter Jason Hammel gave up six hits and one earned run over six innings. "Regardless if I would have sat out or not, I definitely wanted to get out to a good start than off to a bad start", Vargas said. He stole second, took third on a groundout and went home when Mike Moustakas hustled down the line to beat out an infield hit, his first with runners in scoring position this season. "We just couldn't make it happen". He also underwent a heart procedure in February 2015 and was hospitalized again last summer.
Posey was put on the list last week after he was struck in the helmet by a 94 miles per hour fastball from Arizona's Taijuan Walker. The Giants cleared space on the roster for him by designating backup catcher Tim Federowicz for assignment shortly after batting practice. He is 2-0 with a 0.66 ERA in his first two outings, and tossed 7 2/3 scoreless innings against Oakland his last time out. Royals manager Ned Yost is not reminiscing about the 2014 World Series with the Giants back in town. Despite the slow start, Vargas and the Royals know they have their work cut out against him.