OAKLAND -- Riding the high-energy input from new starting pitcher Jeff Samardzija, the A's completed a four-game sweep of Toronto on Sunday with a 4-2 victory over the Blue Jays.

And now the fun begins. The A's host the Giants on Monday and Tuesday, then play at San Francisco on Wednesday and Thursday. Oakland is in first place, the Giants are a hair out of first place and even if that weren't true, both teams would be geared up for this one.

"Yeah, we look forward to it,'' first baseman Brandon Moss said. "It's the same as when we look forward to when the Rangers come in, the Angels come in. When someone that you have a competitive rivalry with comes in. you get amped up for it.''

So the A's and Giants play every year as part of Major League Baseball's "natural rivalry'' program. And while some natural rivals are anything but, the description fits the A's and Giants well.

For Oakland, the Giants may as well be an American League West team for as much drive as the A's put into it. And given how many times the two teams play in Arizona each spring and in the preseason Bay Bridge series, the teams know each other very well.

"It always makes for an interesting series,'' Moss said. "Both cities have unique ways of supporting their teams. They come out, they make it loud, they make it feel like a football atmosphere.

"When you get these two teams on the field, you can't help but feel that energy. That's what makes it fun.''

Moss didn't play in the last two games of the Toronto series thanks to an ankle injury, and the A's were concerned enough about the injury that Moss had an MRI on Sunday morning. Both the player and the team were buoyed by the results that the left ankle is structurally sound. Moss hopes to play Monday, and manager Bob Melvin said he could use Moss as the designated hitter in the opener against the Giants.

Part of the fun Moss was talking about comes from winning. The A's have been doing a lot of that, including sweeping the Blue Jays this weekend. Samardzija, picked up from the Chicago Cubs along with fellow right-handed starter Jason Hammel, made his A's debut Sunday and pitched seven innings, giving up one run and getting his first win in the American League.

"I was very excited,'' he said.

It took him almost two months to get his first win with the Cubs, and when he did, he beat the Giants on May 26. He won't pitch in these four games, but he will be an interested viewer.

"When you come in, you don't want to mess it up,'' Samardzija said. "They were doing just fine without me. I don't want to come in and change anything and change the atmosphere. I just want to come in make a seamless transition into this team and we'll see what happens.''

The A's made it as easy as they could on Samardzija. They scored once in the second inning on a Craig Gentry infield hit for an RBI, then twice in the fourth on RBI singles by Nate Freiman and John Jaso. The pitcher had gotten as many as three runs from the Cubs in just six of his 17 starts, so this was a baseball oasis for the right-hander.

He made the most of it. After the first inning, he didn't give up a hit until the sixth, when two hits with one out produced a run. Samardzija stopped the bleeding there with a couple of grounders, then struck out the side in the seventh before turning the game over to the Oakland bullpen.

"He fits in very well here,'' Melvin said. "That performance was terrific.''

  • Third baseman Josh Donaldson continues to battle back soreness, and it was exacerbated a bit by his catch at the tarp in foul territory Saturday so he was the A's D.H. on Sunday.

  • Hammel was due to arrive in Oakland later Sunday and wasn't at the series finale with the Blue Jays. As a result the A's won't have to make a roster move with him until Monday. The addition of Hammel could force left-handed starter Brad Mills (1-1, 4.41 ERA in three starts) off the roster.

  • Seattle manager Lloyd McClendon said he's going to give his ace, Felix Hernandez, an extra day off this week specifically so he can face the A's in Safeco Field on Friday. Hernandez is 2-0 with a 2.49 ERA in three starts against the A's this season and 17-7 with a 2.64 ERA for his career against Oakland.

  • Stephen Vogt is limping a little with a foot injury but was able to go first-to-third in the fourth inning, eventually scoring Oakland's second run. He also ran hard on a triple in the seventh.

  • The last time the A's swept the Blue Jays in a four-game series was May 22-24, 1981.

    For more on the A's, see John Hickey's Inside the A's blog at ibabuzz.com/athletics. Follow him on Twitter at twitter.com/JHickey3.