When the Marlins inked Wei-Yin Chen to a five year, $80 million deal this offseason they weren’t signing an ace or a workhorse. During his four previous seasons, Chen registered an ERA-, FIP-, or xFIP- better than 90 just once and he maxed out at 192.2 innings in 2012. Chen made a name for himself from 2012 to 2015 as an exemplar of consistency. Above average, but not great. Reliable, but not remarkable.

For $80 million, an opt-out clause, and a vesting option, the Marlins added someone worthy of slotting in behind Jose Fernandez without tying up significant payroll in one of the offseason’s superstar pitchers. Chen probably wouldn’t have been noticed walking down the street in any major-league city other than Baltimore, but front offices and coaching staffs certainly knew the value he could bring to one of those cities.

Yet the early returns on Chen have been somewhat disappointing for the Marlins. He’s running a career worst ERA-, FIP-, cFIP, and DRA over his first 15 starts of 2016. The only major run estimator by which he hasn’t suffered so far this year is xFIP-, which provides a very easy entry point into his struggles: it’s the home-run rate, mostly.

Chen’s never been known for his home-run prevention, registering a HR/9 above the MLB average in each of his major league seasons. Part of that has to do with pitching in Baltimore and in the AL East, but he’s someone who allows a greater share than most of batted balls in the air, and home runs can often come with that territory. This year, his home-run rate has increased at a rate even greater than the MLB average. Granted, the difference between his 2016 HR/9 and his career average HR/9 is something like four home runs over his 86.1 innings this year. Those four home runs happened, but it’s not like we’re looking at an Anibal Sanchez-level event here.

Combine a few more dingers with a slightly lower left-on-base percentage (LOB%) and it’s perfectly easy to see why Chen’s ERA, FIP, cFIP, and DRA are all worse in 2016. His results are objectively worse. The question is if his results are worse due to normal variance and aging or because he’s actually doing something different. I believe the answer is a mixture of both.

First, Chen’s stuff isn’t quite as sharp this year in two important ways. His fastball velocity is down noticeably in 2016 — and, while there are plenty of pitchers who gradually lose velocity without tanking, this is the first time Chen has experienced such a decline. It stands to reason that even a pitcher who is capable of weathering such a storm might stumble when the velocity first vanish.

In addition to losing velocity on his fastball, Chen’s slider lacks the depth of previous seasons and has drifted a bit into cutter territory.

And beyond the prospect of slightly reduced stuff, Chen is also taking a much different approach when it comes to pitch location. Here’s a look at his pitch location through the 2015 season compared to 2016:

Chen has almost totally abandoned the top part of the zone. In identifying this trend over at Fish Stripes, Michael Jong remarked that this is a Marlins philosophy and is likely not something Chen just wandered into on his own. What’s particularly weird about this development is that Chen was successful particularly because of how well he navigated pitches up in the zone. As Jong and others have documented, Chen’s pop-up rate had been among the best in the league. And as you likely know, infield fly balls are the best kind of batted ball because they almost never fall for hits. They are essentially the same as strikeouts.

From 2012 to 2015, Chen ranked 13th among pitchers with at least 300 innings pitched in pop ups per batted ball (4.65%). In 2016, he’s at 1.49% and his 3.15-point decrease is the largest among pitchers to have recorded at least 300 innings in the first sample and 50 this year. Chen’s drop off equates to about eight or nine fewer pop ups so far. If you translate that to strikeouts, you’re taking about a two- or three-point change. In other words, losing the pop ups is a big deal, and if it’s intentional, he should probably knock it off.

Yet while the stuff and pitch location stand out after a straightforward evaluation of his season, there’s another factor hiding in plain sight. His opponents seem to have learned about his platoon split.

Wei-Yin Chen wOBA Against Year vs LHH vs RHH 2012 0.298 0.323 2013 0.298 0.341 2014 0.298 0.326 2015 0.250 0.348 2016 0.300 0.344

While his performance against lefties has regressed from his career-best mark in 2015, Chen’s allowing a pretty similar divide in 2016. The difference, however, is that teams have finally decided to do something to exploit this.

Wei-Yin Chen Batters Faced Year % LHH 2012 26.9% 2013 23.6% 2014 24.5% 2015 23.5% 2016 16.2%

He’s faced about 26 fewer left-handed batters in 2016 than you might expect based on his career norms. Assuming teams are generally subbing out their weaker LHH against him, you could easily imagine this playing a role as well.

Chen isn’t pitching so poorly as to call for his removal from the rotation. He has a similarly roughly stretch in terms of runs allowed in late 2013/early 2014 and has had similarly rough FIP stretches, as well.

But while the overall outcomes aren’t concerning enough to warrant any specific action or panic, there are definitely things worth watching as Chen heads into the second half of his first season in Miami. His fastball velocity is down, his slider doesn’t have as much depth, and he’s throwing pitches low in the zone like never before. He’s not getting outright rocked, but more home runs and fewer pop ups are never good. This is a different Chen that we saw in Baltimore and it’s probably wise to shift back to the guy he was when he wore the other black and orange uniform.

Although, even if Chen does revert back to his last restore point, it’s probably too late to keep teams from stacking their lineups with righties. If that continues, he’ll need to call on his changeup and curveball more so than he has already this year. Pitchers have bad stretches and bad seasons without becoming bad pitchers, but with the Marlins in the race and Chen thinking about free agency again after 2017, it’s probably worth exploring a way back to his old ways.