Longtime readers know I have a particular fondness for rookies, and it turns out that digging into 5 of them earlier this week wasn't enough to fully scratch my itch for now. Below are some expanded thoughts on 3 more.

Reminder to reach out on Twitter anytime @toomuchtuma. All stats entering Tuesday.

Steven Kwan, OF, Guardians

I must admit that I more or less abandoned the Kwan Brigade back in May. After being one of the best stories in baseball throughout April, Kwan's production began to nosedive in the season's second month. He has since come roaring back.

Take a look at his wRC+ by month:

• April: 176

• May: 55

• June: 134

• July: 117

• August: 157

Kwan has proven to be much more than just a flash in the pan, and he's done so in impressive fashion. The first thing I look for when trying to figure out if a breakout player's skill set has improved, and whether or not their production is sustainable, is a reason why.

We have one with Kwan, whose tremendous opening act in April forced pitchers to adjust their approach to him, and he has since adjusted back.

Kwan's batting eye fueled his initial success. Pitchers weren't throwing him strikes and he simply wasn't swing at balls. That's a strong baseline for any hitter. The great ones combine it with damage on contact, which is where Kwan's 1st percentile hard-hit% became an issue.

Pitchers began pounding the strike zone against him, and as you can see in the chart above, his wOBA suffered for a while as a result.

One of the issues for Kwan was that his batted balls became predictable. Through the end of May he was pulling 43.5% of his grounders and line drives, per Fangraphs. Just 18.8% of these batted balls went to the opposite field. So teams began shifting him as well.

Since June 1, however, he has pulled just 36.3% of grounders/liners while going oppo 24.4% of the time. Kwan made himself un-shiftable. When combined with an elite batting eye and plus-plus contact skills, he's able to get on base in a variety of ways.

And that's Kwan's why. He has shown the ability to make an adjustment at the big league level, which is why we can buy into his overall success. Add in strong defense and base running, and Kwan currently ranks 4th in fWAR among rookie position players. He's legit.

Jeremy Peña, SS, Astros

The background on Peña is that he would've ranked much higher as a prospect if it hadn't been for the lost minor league season due to the pandemic. He reportedly bulked up during the shutdown and then lost more time in 2021 due to an injury. The public didn't know much about him entering this season, but the Astros clearly believed in him enough to let Carlos Correa walk.

I bought in to his initial success as he was hitting everything hard while playing elite defense early on. Similar to Kwan he always profiled better as a real-life player, but a 24-year-old shortstop with a 134 wRC+ through the season's first 2 months looked like a cornerstone dynasty player.

In hindsight, I should've been more skeptical of the plate discipline. Peña had a 5.8 BB% and a 22.5 K% through June 1, which is fine, but lurking under the hood was a 35.4% chase rate and a 14% swinging strike rate that was 23rd worst in baseball.

As the season has gone on, Peña's plate discipline has only worsened. Since June 3rd he's batting .218/.255/.364 (74 wRC+), though it at least comes with 8 homers and 4 steals. His swinging strike rate spiked to 17.4% during this stretch and he has chased pitches outside the zone 42.6% of the time. Not good.

Peña's early-season whiff rate wasn't ideal, but it was livable if he stuck to swinging at his pitches. Opposing teams have either found a hole in his swing or a tendency he can't quit, but regardless a turnaround starts with becoming more selective. I remain invested in Peña in dynasty formats, though I've pumped the breaks on valuing him as a top-50 overall player.

Riley Greene, OF, Tigers

Greene isn't off to a hot start to begin his big league career, and it's mainly due to the same issue Alek Thomas is suffering from. Simply put, Greene isn't pulling enough of his fly balls. Among hitters with at least 35 fly ball events, Greene's 5.1% pull rate is third worst in the league. It's lower than Thomas' even.

The 21-year-old is slashing .234/.296/.349 (86 wRC+) with 4 homers and 1 stolen base entering Tuesday. He's been caught stealing 4 times. Unfortunately for Tigers fans, Greene looks like he could benefit from some more seasoning in Triple-A. Fellow preseason top-5 prospect Spencer Torkelson suffered a similar fate earlier this summer.