When a rebuilding club begins its transformation into playoff contender, one can usually identify certain players who emerged during the team’s lean years and made that transformation possible. In the case of the Cubs, for example, that player is Anthony Rizzo. For the Astros, that player is Jose Altuve. For the Phillies, that player might be Odubel Herrera. The former Rule 5 pick is now in his fourth year with Philadelphia, and he has a contract that could keep him with the team for another five seasons beyond this one. He’s been the best player — averaging 3.5 WAR per year — on Phillies teams averaging 95 losses. He might now be the best player on a team that appears to be reversing its fortune and contending for the first time in a half-dozen years.

It would be fair to call Herrera’s 2017 campaign — despite an average offensive season, solid defense, and three wins at 25 years old — a disappointment. After two seasons during which he flirted with four wins, a drop in what should be his prime might have been slightly concerning. However, Herrera really just had a poor two months to start the year. As the calendar turned to June, Herrera was hitting .218/.262/.326 with a 48 wRC+ in 206 plate appearances. The rest of the way, he slashed .318/.361/.526 with a 130 wRC+ in 357 trips to the plate. Even including a couple rough weeks to end last May, Herrera has a 126 wRC+ over the past calendar year and 4.4 WAR, ranking 28th among position players and including a rolling mark that is likely to rise over the next few weeks.

This season, Herrera is hitting .361/.431/.558 with a 172 wRC+ and 1.9 WAR. He’s aided partially by an unsustainable .398 BABIP, but even as that figure regresses, it is probably fair to call what we are seeing a breakout, as Herrera posts what would be career bests in strikeout and walk rates as well as isolated power. To help determine the source of Herrera’s breakout, let’s take a quick look at what Herrera has done in the past with a 40-game rolling timeline. Let’s start with wRC+:

This graph alone might be cause for some skepticism regarding a Herrera breakout. After all, he’s hit his current mark or come pretty close at some point in each of the past three seasons. We’ve seen tears like this before from Herrera. Let’s try to look at some of the individual components that could lead to a big upswing in offense. First, since Herrera’s BABIP is .398, let’s look at his rolling BABIP since entering the big leagues:

Before this season, whenever Herrera had authored huge offensive surges, they were reliant on a BABIP even higher than his current mark — and, on the scale above, the BABIP performance often outstripped the offensive performance overall. There have also been occasions, like at the end of 2015, when he posted remarkably high BABIPs but just above-average hitting numbers. For a short time last season and thus far this season, the offensive surge as been even better than his high BABIP allowed previously. Let’s move on to walk rate:

Herrera has posted higher walk rates over a time in the past. Back in 2016, a very high walk rate looks directly associated with one of his higher offensive peaks. Interestingly, his production near the end of last year and in the first quarter of this season is considerably higher on the graph than his walk rate. So how about strikeouts?

For many players, strikeouts don’t matter all that much. That doesn’t appear to be the case for Herrera. As a player who sports a high BABIP generally, the more often he puts the bat on the ball, the better he performs. His high-water batting marks all came when he was striking out in 20% of his plate appearances or less, while his low batting marks have been generally accompanied by strikeout rates of 25% or more. On to power via isolated slugging:

Back in 2015, Herrera had a brief power surge that coincided somewhat with an offensive boom, though he wasn’t walking much at the time. When he had things going in 2016, he wasn’t hitting for much power at all. Late last season, he was showing off a ton of power along with decent walk and strikeout numbers. So far this season, his power is down a bit from his high point last year, but his walks and strikeouts are even better. It looks as though, if you stretch things back into last season, Herrera is putting everything together for the first time in his career. Even if the BABIP should drop by 40 points, if the rest is sustainable, he’s looking at production about 30% above average the rest of the way and 40% when you factor in his start. With good play in the outfield, that’s a six-win player.

If you have any interest in the trivia of the game Herrera might be of interest, as he’s also chasing Derek Jeter for the longest on-base streak to begin a season (not counting errors). Here are the longest such runs in history, per Baseball-Reference.

He’s still a long ways off from Ted Williams’ streak at any point during a season, but he’s only a few more weeks away from Jeter. There are a lot of really good hitters on this list, including seven Hall of Famers, before you get to Jeter and Albert Pujols. Odubel Herrera is an impressive baseball player on his way to what could be his best season in the majors. If the Phillies are going to stay in contention as the season goes on, the team will need him to keep producing.

Philadelphia has had a lot of great prospects emerge over the past few seasons — J.P. Crawford, Rhys Hoskins, and Scott Kingery for example — but Herrera (whom they acquired from Texas for basically nothing) might be the most important piece in aiding Philly’s return to the postseason.