After winning 20 of their last 29 games, the San Francisco Giants are by themselves in first place. The entire pitching staff seems to be peaking at the same time, everything about the offense is aggressive, and on defense they’ve gone from cringeworthy to competent over the span of less than a month.

They’ve done it with a mix of familiar contributors and new faces, including an entirely different outfield than last season. Cody Ross, one of the streakiest players in the game, is in Boston. Another hot-and-cold guy, Nate Schierholtz, has been relegated to fourth outfielder status. Randy Winn, well, he’s been gone for a while. But he sure was streaky (and classy).

Even without Ross and with Schierholtz watching most of the action, the Giants have put together a considerable number of streaks this season.

Pablo Sandoval: 20-game hitting streak

Angel Pagan: 20-game hitting streak

Angel Pagan: 12-game hitting streak

Angel Pagan: 28-game home hitting streak (franchise record)

Melky Cabrera: 11-game hitting streak

Melky Cabrera: Four consecutive multihit games (three different times)

Ryan Vogelsong: 11 straight quality starts (and counting … only one of his 14 starts failed to reach the “quality” plateau, when he gave up 4 ER over 6 IP in Cincinnati on April 26)

Sergio Romo: 13 straight scoreless appearances to start the season

Pitching Staff: Four straight shutouts

Matt Cain: 27 consecutive outs (perfect game vs. Astros)

One of the reasons why the Giants have sec0nd-best record in the National League — even though they’re currently sixth in the NL in run differential — is their longest losing streak is only four games. That monstrosity only happened once, when they lost every day from May 1-4 to fall to 12-14. They’ve only lost three games in a row one other time: when they got swept in Arizona to open the season.

So far, the Giants aren’t a team that reels off long winning streaks, either. The Giants have two four-game winning streaks this season, both coming in June. That includes their current four-gamer, courtesy of Madison Bumgarner.*

Should Giants fans be happy with a team as steady as San Francisco has been? Absolutely, especially if the alternative is watching a team like the Miami Marlins, who’ve had one seven-game winning steak but have also suffered through three six-game losing streaks.

The question now, with everyone relatively healthy and a team full of players that have shown the potential to put forth superlative efforts for several games consecutively, is whether the Giants can pull off some impressive winning streaks of their own. To expect Cain to continue the shutout streak would be unfair, but the Giants certainly have a decent shot at their first five-game winning streak.

*I was at the Warriors’ practice facility last night for the NBA Draft, but I watched Madison Bumgarner’s performance in pieces over last night and this morning. It goes without saying that a one-hitter was impressive, but the way he commands all of his pitches (his slider, in particular) and pitches inside so effectively … it’s just amazing that the guy is 22.

The way Bumgarner handled Joey Votto was clinical (when Votto turned around and asked C.B. Bucknor whether not not the slider he swung through would’ve been called strike three — and then nodded after hearing it would’ve been — it was the kind of scene one will only see with one of the best pitchers in baseball on the mound).

Now Bumgarner has broken through the complete game barrier for the first time. Considering the fashion in which he did so, it’s hard to even conceive of what could be next for the man the Giants have locked up for up to seven years and a total of $56.5 million.

In case you care about such things, ESPN’s Cy Young Predictor now has Bumgarner in third with 91.2 points. Matt Cain’s in second with 97.4, behind knuckleballer R.A. Dickey (109.2).

Rob Neyer and Bill James didn’t add “perfect game” as a variable. What should those be worth? About 12 points?