The last time the San Francisco Giants visited Busch Stadium, the night was supposed to end in glory, jubilation and celebration for the Cardinals and their faithful. But little did St. Louis know that Barry Zito had sold his soul to the baseball gods for one last opportunity to pitch like it was 2002 again.

Fortunately for the Cardinals, Zito already pitched on Thursday in San Francisco, which means St. Louis won’t have to re-live any bad memories when the Giants come to town this weekend for a three-game series. Whatever witch magic Zito used in Game 5 of the NLCS to shut out the Cardinals last year has surely vanished by now.

In the grand scheme of things, this series against the Giants is a small blip on the Cardinals’ 2013 season. There’s still a lot of baseball to be played and, after all, the All-Star Break is still a month and a half away.

But throughout the course of a 162-game schedule, there are certain mile markers in which to stop and observe. This series is one of them.

Over the course of May, the Cardinals have feasted on the likes of sub-.500 teams in the Brewers, Mets, Dodgers, Cubs and Padres. But nobody in Cardinal red should apologize. For those who have paid attention, this is clearly the best team in the National League. They have the best starting rotation, one of the most dangerous lineups, as well as an improving bench and bullpen situation (save for Mitchell Boggs blowing yet another save on Thursday night). But the Giants will provide the Cardinals with their best challenge since the Reds left town in early May, and for reasons you wouldn’t think.

San Francisco has been rather baffling this season. A club that has won two of the last three World Series by virtue of its pitching has suddenly done an about-face. Instead of relying on its rotation, San Francisco has won in spite of its pitching.

Matt Cain, whom the Cardinals will face tonight, owns a 4-2 record but has been brutal for much of the season. In his possession is a 5.00 ERA, and he’s allowed 13 home runs in just 11 starts. Teams have jumped on him early, as he’s given up at least one run in the first inning in four of his 11 starts and has allowed at least one runner to reach base in nine of his 11 outings. Compared to the last four seasons, his walk rate is up and he’s having problems with his delivery, too.

Meanwhile, Madison Bumgarner has been the Giants’ most consistent pitcher this season, but the team has lost four of its last five games with him on the mound. He also had a rough outing in Colorado on May 17 when he allowed nine runs (seven earned) on eight hits over just 4 2/3 innings of work. With Tim Lincecum continuing to struggle and Ryan Vogelsong out with a broken hand, the Giants’ pitching has been shockingly bad through the first two months.

And yet because of their hitting, they remain four games above .500 and just 1.5 games back of the Diamondbacks in the NL West. They’re fourth in the league in batting average, 12th in runs, 12th in on-base percentage and 14th in slugging percentage. Outside of the batting average, those aren’t eye-popping numbers, but Hunter Pence, Pablo Sandoval and Buster Posey have all flashed power, while Marco Scutaro (the Cardinals have not-so-fond memories of him from last year’s NLCS, too) leads the team with a .330 average. Brandon Crawford (25 RBIs) has also been one of the most productive eighth-place hitters in all of baseball and, amidst a poor defensive team, he flashes an excellent glove at short, too.

The Giants have also shown a propensity for winning games in the later innings. Following their victory over the A’s yesterday, 16 of the Giants’ 29 wins this year have been of the come-from-behind variety. They don’t panic, they don’t play in too many blowouts, and they feel comfortable when trailing late.

The Giants have lost five their last eight games, but even so, they provide a nice test for Shelby Miller, Adam Wainwright and Tyler Lyons. While he hasn’t pitched to form, Matt Cain is still Matt Cain and lefties have regularly been an issue for St. Louis hitters, so it’ll be interesting to see how the Cards fare against Bumgarner on Saturday. (San Fran also boasts two excellent left-handed relievers in Jeremy Affeldt and Javier Lopez, so the battle of pens will be fun to watch as well.)

The Cards should, at the very least, take two of three this weekend. They have the better rotation, the better offense, and the better overall defense. They’re clearly the team to beat in the National League and they already won two of three earlier this year in San Francisco.

But this isn’t the Mets coming to town. It’s the defending champs, and the Cards still have some demons to exercise against this San Francisco team.

Let the games begin.