They were good as rookies. This season? Even better

Always remember that player development is not linear.

It would be awesome if every rookie and top prospect hit the ground running upon reaching the Majors and continued to improve from month to month and year to year. That's not realistic.

However, there are some players who have built upon a successful 2023 rookie campaign with even better numbers this season. Here are seven second-year standouts who fit that description.

All stats updated entering Saturday.

Gunnar Henderson, SS, Orioles
The reigning American League Rookie of the Year is performing like an MVP candidate in 2024. He owns a .926 OPS and is one of only two players (Mike Trout) with double-digit homers and at least five steals this season. The AL Player of the Month for March/April, Henderson is absolutely hammering baseballs; his average exit velocity (94.9 mph) and hard-hit rate (56.4%) rank inside the top 10 among hitters with at least 50 batted balls.

Henderson is doing especially significant damage against breaking pitches -- curveballs and sliders -- as his .805 slugging percentage is second-best in baseball (min. 30 plate appearances ending on breaking balls). That's a big upgrade from his respectable .479 slugging against breaking balls last season. If the 22-year-old keeps this up, he could become just the fifth player to win Rookie of the Year and MVP in consecutive years, joining Cal Ripken Jr., Ryan Howard, Dustin Pedroia and Kris Bryant.

Jordan Westburg, 3B, Orioles
OK, we promise this list isn't just a bunch of O's. But after a rookie year in which his production was the definition of average (100 OPS+ through 228 plate appearances), Westburg has emerged as a real threat while often batting in the lower half of Baltimore's lineup. Since April 10, he is slashing .342/.395/.582 in 20 games. His 1.008 OPS during that span is tied for 11th in MLB (min. 80 PA).

Taking some inspiration from Henderson, his partner on the left side of the Orioles' infield, Westburg has simplified his setup in the batter's box. That mechanical change has allowed him to be more on time with his swing, as MLB.com's Brent Maguire recently detailed. The results so far have included fewer strikeouts, fewer ground balls, more line drives and an expected batting average of .339, third-best among hitters with 50 batted balls. Plus, Westburg has already accrued more outs above average at the hot corner this year (two) than in 2023 (one).

Elly De La Cruz, SS, Reds
We were all introduced to De La Cruz's prodigious power and blazing speed in 2023. He has seemingly supercharged those abilities this season. His April included eight homers and 19 stolen bases, making him the first player with that many home runs and steals in a calendar month since at least 1901. But De La Cruz is doing more than relying on his natural physical gifts.

As MLB.com's Thomas Harrigan presented in an in-depth breakdown, the Reds' superstar is making better swing decisions and has become a more efficient base stealer. That's put him on pace for an outrageous 41 homers and 96 steals. De La Cruz still has whiff and K rates above 30%, but with an elite barrel rate (16.5%) and 99th percentile sprint speed, Cruz could be authoring a season the likes of which we've never seen before.

Patrick Bailey, C, Giants
Bailey's defense was nearly unmatched in his rookie year; his fielding run value of +18 runs trailed only Rockies outfielder Brenton Doyle (+20). But the value of Bailey's bat lagged far behind his glove as he turned in a 78 OPS+. That number is up to 134 this year, and much of the credit goes to Bailey's greater frequency of desirable contact.

Besides raising his hard-hit rate by 10 percentage points, Bailey's sweet spot rate -- his percentage of batted balls with a launch angle between 8 and 32 degrees -- is an MLB-best 53.2%. That's a 17-point jump from last season, which is the second-greatest increase from year to year among qualified hitters. Now a much more well-rounded player, Bailey is already up to 1.1 bWAR this season. He had 0.8 bWAR through 97 games last year.

• Bailey exits with blurry vision as Giants drop opener to Phillies

Bryce Miller, RHP, Mariners
Pitchers experiment with new pitches every year, but those new additions don't often work out as well as Miller's new splitter has for him. His MLB introduction had its fair share of successes, including an opening stretch in which he allowed only four runs through his first five starts. But as the 2023 season aged, it was clear that Miller needed another weapon to keep hitters from sitting on his effective 95 mph fastball. So, he folded the splitter into his repertoire this winter, and the results have been spectacular.

That pitch, which is getting 4.4 inches more drop than similar splitters, has led to only four hits -- all singles -- with 13 K's in 32 at-bats. It's a big reason why hitters are batting only .156 with a .311 slugging percentage against the right-hander.

Anthony Volpe, SS, Yankees
Volpe has fallen back into some bad habits over his past eight games. He has struck out 11 times in 32 at-bats and logged a 34.3% whiff rate over that period. Even with this little bump in the road, Volpe is still more of an offensive force than last year, when he became the first Yankees rookie to post a 20-20 season.

On pace for 14 HRs and 33 steals, Volpe has seen his OPS+ go from 81 to 113 in his sophomore season. The 23-year-old has lifted his average (.264) and OBP (.349) more than 50 points thanks largely to a decrease in his swing-and-miss. Volpe's 20.8 whiff rate is about 8 percentage points less than in '23. His chase and strikeout rates have also dipped while his walk rate is now in double digits (10.1%). Not to mention that Volpe's defense, which led to +1 OAA last year, has taken a leap as well. Perhaps a second Gold Glove is in his future.

Javier Assad, RHP, Cubs
Assad is the most unheralded player on this list. He was never among the Cubs' top 20 prospects, much less one of the top 100 in the league. With a six-pitch mix and a four-seamer that averages 92 mph, "crafty" would be an apt adjective for the 26-year-old. He worked his craft on opposing hitters last season, registering a 3.05 ERA in 32 games (10 starts) as he shifted between the bullpen and the rotation.

He won a starting spot out of Spring Training this year, and the Cubs have needed every bit of his contributions while lefty ace Justin Steele has been sidelined with a hamstring injury. Assad has responded by posting a 1.97 ERA and a .541 opponents' OPS through six starts (32 innings). He hasn't allowed more than two earned runs or five hits in any of his turns. He possesses one of the most valuable sinkers in the game, and Assad's overall value (1.3 bWAR) trails only fellow starting pitcher Shota Imanaga (1.8) for the team lead.