The Giants have the oldest lineup in baseball -- the average age of their hitters this season is over 31 years old -- so it's a good thing two of their veteran stars have found the fountain of youth.

Buster Posey and Evan Longoria are hitting like years-younger versions of themselves, a big reason why San Francisco, not the Dodgers or Padres, finished April in first place in the National League West.

The 34-year-old Posey is hitting .359/.423/.688 with six homers and a 1.110 OPS. The 35-year-old Longoria is hitting .275/.390/.522 with four homers and a .912 OPS.

Posey has a 207 OPS+ -- meaning he's been more than twice as good as a league-average hitter (100). Longoria has a 155 OPS+. Posey and Longoria are one of 10 sets of MLB teammates with a comparable number of plate appearances who have been at least 50% better than league average this season.

Teammates with 150 OPS+ or better in 2021
Minimum 70 plate appearances each
Byron Buxton (267)/Nelson Cruz (195), Twins
Mike Trout (259)/Jared Walsh (190)/Shohei Ohtani (151), Angels
J.D. Martinez (217)/Xander Bogaerts (170)/Rafael Devers (160), Red Sox
Buster Posey (207)/Evan Longoria (155), Giants
Jesse Winker (176)/Nick Castellanos (161), Reds
Justin Turner (175)/Chris Taylor (157), Dodgers
José Ramírez (168)/Franmil Reyes (153), Indians
Yuli Gurriel (168)/Yordan Alvarez (156)/Michael Brantley (150), Astros
Jesús Aguilar (161)/Jazz Chizholm Jr. (152), Marlins
Trent Grisham (159)/Fernando Tatis Jr. (157), Padres

Their resurgence kind of came out of nowhere. Posey and Longoria were perennial MVP-caliber players once, but they haven't looked this good in a while.

Longoria was below average at the plate over his first three seasons in San Francisco, posting a 96 OPS+, compared to the 125 OPS+ he had in 10 years with the Rays. Posey was going through declining production even before he missed an entire season in 2020 -- his OPS+ dropped from 127 to 108 to 83 from 2017-19, and he only averaged six homers from '18-19, the same total he reached in 17 games in '21.

Posey and Longoria powering their team is a great throwback to their superstar days. It's fun to see the two of them raking.

They're both doing a great job of both hitting the ball hard, and driving it in the air. Posey and Longoria rank near the very top of the league in hard-hit + sweet-spot contact -- those are balls hit both 95 mph or harder and in the best line drive/fly ball launch angle range of 8-32 degrees.

Highest rate of hard-hit + sweet-spot contact, 2021
Of 223 hitters with 45+ batted balls

1. Salvador Perez (KC): 35.1%
2. (tie) Nick Castellanos (CIN): 34.9%
3. (tie) Aaron Judge (NYY): 34.9%
4. Evan Longoria (SF): 34.7%
5. Bryce Harper (PHI): 31.1%
6. Buster Posey (SF): 30.8%

Hard-hit: 95+ mph exit velocity. Sweet spot: 8-32 degree launch angle.

Posey has simplified his batting stance, and he's driving the ball all over the field. He doesn't quite look like the classic Posey -- the open-stanced, deep-kneed, bat-draped-flat-over-the-shoulder Posey of years past has been replaced by a more straight-up, vertical-bat Posey who has to do less to get into his swing -- but he sure is hitting like the classic Posey.

Posey is squaring the ball up at a completely different level than the last time he played.

• His 46.2% hard-hit rate is 10 percentage points higher than it was in 2019, and the highest it's ever been since Statcast started tracking in 2015.
• His 46.2% sweet-spot rate is one of the 10 best in baseball, and 10 points higher than it's ever been since 2015.
• His 11.5% barrel rate -- that's how often he hits the ball with a perfect combination of exit velocity and launch angle -- is almost twice as high as any he's ever posted in the Statcast era (6.9% in 2016).
• He ranks in the 94th percentile of MLB in both expected batting average and expected slugging percentage based on his quality of contact. He's never ranked in the 90th percentile or better in both categories.

And he's hitting everything. Posey is batting .349 against fastballs (four-seamers, sinkers and cutters), .400 against breaking pitches (sliders and curveballs) and .333 against offspeed pitches (changeups and splitters).

Longoria is also crushing the ball.

• His average exit velocity of 95.9 mph is one of the highest in baseball and four full mph higher than any other season of Statcast tracking.
• He's already hit a ball 113.2 mph this season, nearly two full mph harder than any other ball he's hit under Statcast tracking.
• He's barreling 18.4% of his batted balls, in the 94th percentile of MLB.
• His 63.3% hard-hit rate is second only to Giancarlo Stanton and makes him one of the biggest gainers from 2020-21 (up 17 percentage points from 45.2% in '20).

Highest avg. exit velocity, 2021
Of 224 hitters with 45+ batted balls

1. Giancarlo Stanton (NYY): 98.7 mph
2. Aaron Judge (NYY): 97.4 mph
3. Pete Alonso (NYM): 97.0 mph
4. Rowdy Tellez (TOR): 96.7 mph
5. Evan Longoria (SF): 95.9 mph

Biggest increases in hard-hit rate, 2020 to '21
Of 194 qualifying hitters

1. Avisaíl García (MIL): +18.5 points (37.1% to 55.6%)
2. Evan Longoria (SF): +18.1 points (45.2% to 63.3%)
3. Pete Alonso (NYM): +17.7 points (41.2% to 58.9%)
4. Starling Marte (MIA): +17.4 points (30.3% to 47.7%)
5. Rowdy Tellez (TOR): +16.9 points (45.3% to 62.2%)

Longoria's underlying numbers were actually better than you might think last season -- he ranked in the top quarter of the league in exit velocity, barrels, hard-hit rate, expected batting average and expected slugging percentage -- but they weren't anything like this.

His performance has been driven by a few things in particular:

1. Killing fastballs, which he's batting .357 and slugging .762 against with all four of his home runs, including three to the opposite field.
2. Getting the ball off the ground -- he's chopped almost 15 percentage points off his ground-ball rate, which is down from 50.3% to 36.7%, while he's hitting close to 60% line drives and fly balls.
3. Better selection at the plate -- Longoria has cut his chase rate by about 10 points, from 27.8% to one of the lower rates in baseball at 18.4%, while also swinging at more pitches in the strike zone than last year.

With Longoria and Posey making such strong contact, it's nice that the stat sheet is falling in line. The young phenoms all over the game today are amazing to watch, but Longoria and Posey used to be two of those young superstars themselves, and it's good to see them reminding us of it again.