"There's not too much we don't already know about him," said Stewart, who played for the Giants in 2011. "But as far as what's the stuff going to look like coming out of his hand, he's obviously a little untraditional out there, you could say, [with] the way he throws. I informed these guys how he likes to throw in certain situations, what his go-tos are [in] certain counts and certain situations throughout the game.
"It's nice that I can relay that to these guys so we kind of have a head start on it."
Bumgarner recorded a 2.91 ERA in his 13-game collaboration with Stewart, who was summoned from Triple-A after Buster Posey sustained his season-ending left leg injury in late May. The left-hander's ERA with other catchers that year was 3.43.
"He has the same competitiveness that he had back then," Stewart said. "Not too many things get under his skin."
Chris Haft is a reporter for MLB.com. Read his blog, Haft-Baked Ideas, and follow him on Twitter at @sfgiantsbeat. This story was not subject to the approval of Major League Baseball or its clubs.