In this case, it means playing the role of stopper as the Giants have lost the first two games of the young season, both by 5-4 margins, and both with the starting pitchers taking the loss.
Cain, who signed a contract extension that will keep him with the Giants and pay him $127.5 million through 2017, will be matched against the defending National League West champion D-backs and right-hander Josh Collmenter, a pleasant surprise for Kirk Gibson's team a year ago.
In terms of resume and paycheck, Cain has the advantage. A two-time All-Star in six-plus seasons of consistency and success, Cain now has the big deal that will keep him in San Francisco. While some might think the big contract will change his focus, Cain says otherwise.
"I feel like I don't need to be motivated that way," Cain said. "I'm going to be motivated by playing."
He'll be playing in hostile territory in this one. With a 69-73 record and 3.35 ERA through 203 career starts, Cain has a 30-38 road record, 18-17 in the past three years.
Dating back to last season, the D-backs will be going for their eighth straight win against the Giants, and Collmenter enters the start almost a year to the day after he made his Major League debut with a win against the Giants on April 17, 2011.
Collmenter had a rough spring -- he allowed as many homers as he had strikeouts, with five -- but he pitched a little better in his final outing, an abbreviated one against the Brewers last Tuesday night. Collmenter has worked hard on his curveball to try and make sure he's got a solid third pitch.
The right-hander finished off his spring with three hitless innings against the Brewers.
Giants: Sandoval third option at catcher
Pablo Sandoval, the Giants' starting third baseman and No. 3 hitter, played 11 games at catcher in his 2008 rookie season and another three in 2009. He won't get that many, but he's set as the emergency third catcher if ever the Giants need someone and both Buster Posey and Hector Sanchez have been used.
Saying he might be "super-sore" the next day, Sandoval is OK with making another appearance sometime at catcher, where he made 176 appearances in the Minors.
"If [manager Bruce Bochy] needs me, I'm there," Sandoval said. "I'm fine with that."
With Ryan Theriot getting the start in the first two games, it's possible Emmanuel Burriss might get the nod at second base Sunday. If he does and the rest of the infield remains the same, the Giants would have an all-homegrown infield.
D-backs: Gibson: Not a big hardware guy
Not surprising to anyone who has listened to his comments as manager the last year-plus, Gibson isn't about individual accolades. He received his 2011 NL Manager of the Year award on Opening Day and has no set plans of what to do with it.
"I haven't really thought about it -- in storage like the rest of them," he said. "I'm not a big displayer. I donated [the 1988 National League MVP trophy] to my foundation and sold it."
Gibson's foundation provides scholarships to Michigan State, his alma mater, and he suggested the Manager of the Year award might be the next thing sold to help fund that foundation.
The D-backs are 2-0 for the fourth time in club history (2000-02) and have started 3-0 only once, in 2000. Aaron Hill, who had his third two-homer game Saturday, said it's a good way to start against a team the D-backs know will be their chief competition for the NL West title.
"They'll be there," Hill said. "It's a long season [and] they're a great team, so we don't look into it. We've got two games under our belt and that's great, but we've got tomorrow to deal with."
How this matchup starts in the regular season isn't always how it finishes, or at least it wasn't last year. In 2010, the Giants won seven of the first nine between the two teams, then the D-backs won seven of the next nine.
After Sunday's finale, the Giants will continue their season-opening road trip in Colorado, where they'll play three games in four days with Tuesday a scheduled off-day. The D-backs head to San Diego for a three-game set that begins Tuesday.