Entering the 2021 season, the general expectation was there would be two competitive teams in the NL West, in the Dodgers and Padres. But halfway into the season, there’s a third team in that division that made an early statement and is still the best team in baseball. The Giants are 52-30, with a .634 winning percentage that is just ahead of the Dodgers for best in the Majors.

They’re tied for the MLB lead in home runs and sport the league’s second-lowest overall ERA, so they’re getting it done on both sides of the ball. They have a plus-103 run differential. There’s no question the Giants have been among the best teams we’ve seen so far this season. But with the unexpected nature of this campaign, it’s a fair question to ask whether this can continue for the full 162 games and into October.

Here’s a look at some of the main factors that have been key to the Giants’ success, and whether they seem sustainable.

The 30-plus crowd

The Giants have gotten significant offensive contributions from at least four players aged 33 or older who were not necessarily expected to help carry the team in ‘21.

Chief among those has been Buster Posey, who, at 34 years old, is having the second-best year of his career by many measures. After electing not to play in 2020 and missing time in ‘19 with injuries after his ‘18 season ended early due to hip surgery, Posey appears to be back to playing at full health for the first time in a while. His current .548 slugging percentage and .327 batting average would each trail only his 2012 MVP season, when he led the Majors in batting average at .336 and slugged .549.

The underlying numbers back up his performance, too. Posey’s 45.2% hard-hit rate would be his highest under Statcast tracking (since 2015), and his .293 expected batting average, based on quality of contact, is 93rd percentile in MLB. His .520 xSLG would be by far his highest since ‘15. The NL MVP conversation already has names like Fernando Tatis Jr., Jacob deGrom, Nick Castellanos, Jesse Winker, Ronald Acuna Jr., and others -- and Posey’s is there, too.

Shortstop Brandon Crawford, also 34, is having a similar resurgent season, slugging .537, which would be by far the best of his career, and displaying Gold Glove-caliber defense. He, too, has put up results backed by contact stats -- a 94th-percentile barrel rate and 93rd-percentile xSLG. Posey was voted the NL’s starting catcher for the All-Star Game, and Crawford seems likely to join the Midsummer Classic ranks as a reserve when those are announced Sunday.

33-year-old Brandon Belt and 35-year-old Evan Longoria were having similar strong seasons, but both are currently on the injured list.

Starting pitching acquisitions working out

The Giants have a 3.29 starters’ ERA this season, third-best in MLB, and three notable acquisitions panning out have been key to that group’s success.

The team’s best starter has been Kevin Gausman, who is having one of the best seasons of any starter in baseball, non-deGrom division. His 1.68 ERA is second-best among qualified starters behind deGrom, and his .807 WHIP ranks third. This is his second season in San Francisco -- he signed as a free agent entering 2020, then took the qualifying offer entering ‘21. With the Giants, Gausman has been able to capitalize on changes that began for him as a member of the Reds’ bullpen towards the end of 2018, throwing his splitter more. That’s helped make his four-seamer and splitter two of the best pitches in baseball, and shown that his good 2020 with the Giants was not a fluke.

Another free-agent signing was Anthony DeSclafani, who has a 2.91 ERA for the Giants in 16 starts, a year removed from a 7.22 ERA in 33 ⅔ innings for the Reds in 2020. Just as the Giants have had Gausman throwing his splitter more, DeSclafani’s primary pitch this year has been his slider, which had been his best pitch, instead of his four-seamer which was hit hard in 2020. His slider has been even better than last year, and the four-seamer has been hit less hard in conjunction, too.

The other notable addition was Alex Wood, who has a 3.89 ERA in 14 starts for the Giants. Wood’s season began in mid-April after a back injury, but he’s already thrown more regular-season innings in 2021 than he did in 2019-20 combined for the Reds and Dodgers after a back and shoulder injury.

A solid bullpen

Offense, check. Strong starting rotation pieces, check. The third element that has helped the Giants continue to succeed is a reliable bullpen. Relief pitching can be hard to predict, but the Giants bullpen has mostly been able to back up those starters and lock down wins.

The Giants have a 3.20 bullpen ERA, third in MLB behind only the Padres (2.87) and Cubs (3.08). They’ve been helped by a bounceback season, results-wise, from Tyler Rogers. He had a 4.50 ERA last year in 29 games, though a 3.26 FIP indicated perhaps the results should have been better. This year, he has a 1.36 ERA with nine saves, as another notable acquisition, Jake McGee, has primarily handled closing duties.

McGee, also signed as a free agent like the starters noted above, has 16 saves and a 2.97 ERA. He’s already three saves shy of tying his career high, set in 2014 with the Rays, and is on pace for the most appearances in save situations in his career.

Can this continue?

Those three reasons outline much of what has fueled the Giants success, but is it sustainable? The underlying metrics on both Posey’s and Crawford’s seasons indicate that production should continue, barring injuries. Both are making quality contact, and even though they’re both slugging well above career averages, expected stats back that up. Posey’s playing time has been carefully managed thus far, which has played a role in keeping him healthy, too. If Belt and Longoria can play at the same levels when each returns, that will help, too -- and it isn’t just those players. Austin Slater hit a go-ahead homer for the Giants on Saturday, and Steven Duggar is hitting .313, amongst notable contributions from the under-30 crowd.

Contact stats and FIP seem to indicate that the top three members of the rotation are for real, too, in Gausman, DeSclafani and Wood. Johnny Cueto, at one point a Giants ace, has a 4.00 ERA, but has pitched well enough to keep a homer-happy offense in games. With Logan Webb out in the month of June, the team turned to various other options, most recently Sammy Long.

The bullpen has been one of the better in baseball, and already some of the pitchers involved have changed throughout the year -- and likely could continue to with the Trade Deadline afoot.

If anything, the biggest unknown for the Giants’ continued success is simply the play of the other teams in their division. The Dodgers have gained ground of late and entered Sunday just a half game behind the Giants. The Padres are not too far behind -- four and a half games out from the Giants. Each team has won exactly 22 games against divisional opponents, with various quantities of losses (14 for the Giants, 11 for the Dodgers and 15 for the Padres) -- and plenty more such matchups to come. But there’s no question that thus far, the Giants’ success has been for real.