In the span of a few months, Chris Archer went from midrotation starter to ace to All-Star to Cy Young contender.

He dominated baseball in 2015, racking up 252 strikeouts, a Tampa Bay Rays record. He allowed two or fewer runs in 22 of his 34 starts. He ranked among the top 10 pitchers in Wins Above Replacement.

Archer was as highly regarded as Max Scherzer, Chris Sale, Zack Greinke and David Price. It was reasonable to wonder whether he could one day be as good as Clayton Kershaw. The pages of the Tampa Bay Times and tampabay.com anointed him “the new face of baseball.”

Three years later, the Kershaw comparisons have quieted. He’s no longer the face of baseball. And as of Tuesday, he’s not even the face of the Rays. He’s a guy on the Pirates.

RELATED STORY: Rays trade Archer to Pirates for Austin Meadows, Tyler Glasnow

One way to look at this trade is to say the Rays traded yet another All-Star player.

Here’s another way: They didn’t trade the Chris Archer of 2015. They traded the Chris Archer of 2018.

Archer, who turns 30 in September, hasn’t been experiencing a steep decline. Not by any stretch. He is still an above-average pitcher who at times is a very good pitcher. What he is not, and hasn’t been for quite some time, is a bonafide ace, the type of pitcher you can count on to shut down opponents every fifth day. In fact, in his six full seasons, the Rays have a higher win percentage when he doesn’t start (.499 vs. .453).

“I don’t think he’s a No. 1 starter, personally — or a No. 2,” a National League scout told ESPN’s Jerry Crasnick recently. “It’s not about the stuff. But he’ll make more mistakes than a No. 1 or 2 can afford to make. He can pitch like a No. 1 on any given day or a No. 5 on any given day.”

The numbers back up the scout’s claim Archer’s stuff is still good. He has even increased his overall rate of swings and misses. His strikeout and walk rates are in line with his career averages, as is his velocity. Yet his ERA and batting average against are the highest since his June 2013 callup (he pitched 29.1 innings in 2012).

W-L ERA BAA IP K/9 BB/9 SwStrike%* WAR
2013 9-7 3.22 .223 128.2 7.06 2.66 9.1% 1.3
2014 10-9 3.33 .239 194.2 8.00 3.33 9.3% 3.2
2015 12-13 3.23 .219 212.0 10.70 2.80 12.8% 5.2
2016 9-19 4.02 .235 201.1 10.42 3.00 12.2% 3.2
2017 10-12 4.07 .245 201.0 11.15 2.69 13.4% 4.6
2018 3-5 4.31 .270 96.0 9.56 2.91 13.6% 1.7
*swings and misses/total pitches Source: FanGraphs

So why hasn’t Archer lived up to the lofty expectations of 2015?

The strikeout numbers are hiding something:

Archer’s slider — the pitch that made him a star — hasn’t been as effective as it once was.

Flash back to a game against the Mariners in June. Kyle Seager, a left-handed hitter, was at bat against Archer, a right-handed pitcher, with runners on first and second and two outs. With the count at 1-and-1, Archer fired a 96 mph fastball over the middle of the plate. Seager fouled it off.

The pitch on 1-and-2? You guessed it. A slider.

But Archer left the ball up in the strike zone, and Seager drove it to deep left field for an RBI double. It was his first hit in 17 at bats against Archer.

It’s not just Seager. Lefties across baseball are hitting Archer like they did when he was a rookie. You’d expect lefties to have more success than righties against right-handed pitchers. They have slightly more time to recognize pitches. But until this season that hasn’t been the case for Archer. Righty or lefty, when he has gotten to two strikes, he has put the batter away.

The heat maps below illustrate the difference between 2015 All-Star Archer and 2018 Average Archer. The black box represents the strike zone. The darker colors represent spots a pitcher hits more frequently.

[FanGraphs]
[FanGraphs]

The map on the left shows the location, from the perspective of the catcher, of Archer’s slider to lefties in 2015 and the map on the right shows the location to lefties in 2018.

In 2015, Archer was generating swings and misses because he was consistently locating the pitch just below the strike zone. This season, the pitch isn’t just catching more of the zone — it’s catching the center of the zone. And those few inches make all the difference between strikeout and hit, between seven innings and an early exit, between dominance and danger.

“Sometimes it plays into the lefty’s swing if I don’t execute it,” Archer said. “A slider down and in and under the zone is great but slightly in the zone isn’t that great. The same exact pitch you throw to a righty, you put a lefty in there and it plays into that down-and-in swing. And it’s 89 (mph). It’s a speed to where they can get the barrel to it.”

The results: Lefties have a .283 batting average against him — and a .254 batting average against his slider. That’s more than 80 points higher than it was in 2015.

Fastball Changeup Slider
2013 .294 .316 .212
2014 .250 .273 .186
2015 .275 .235 .171
2016 .295 .250 .175
2017 .322 .314 .214
2018 .372 .227 .254
Source: Brooks Baseball

And corresponding to that increase in batting average is a dip in strikeout rate. From 2015 through 2017, Archer struck out lefties nearly 30 percent of the time. This season, he has struck out them out just over 20 percent of the time.

The quality of contact is better, too. Lefties are hitting Archer’s slider for more power and extra bases, as indicated by opponents’ isolated power percentage, which is the highest of his career and three times what it was in 2015. (Isolated power measures a player’s raw power and tells you how often a player hits for extra bases. You can calculate it by subtracting batting average from slugging percentage.)

Hits Extra Home runs Isolated power
2013 22 9 6 .212
2014 22 6 1 .068
2015 36 12 1 .067
2016 32 10 4 .105
2017 42 11 5 .117
2018 18 9 4 .239
Source: FanGraphs

Manager Kevin Cash said there’s no difference in the movement of Archer’s slider. On average, the pitch has moved toward left-handed batters 3 to 4 inches, and it’s in that range again this season.

“By everything that we have, by all accounts it’s the same pitch,” he said. “When you don’t locate it as consistently, it’s going to get hit.”

Archer is making adjustments. For the first time since 2014, his rate of sliders to lefties has decreased as he continues to mix in changeups. He has thrown changeups to lefties about twice as often as he did in 2015. (Against righties, he’s still primarily a two-pitch pitcher. He’s thrown 10 changeups all season to them. Not 10 percent. 10 total.)

It seems to be working. Lefties are hitting .227 against Archer’s changeup this season and have managed only one extra-base hit.

Perhaps the changeup can help Archer return to ace form, particularly if he continues to struggle locating his slider. But we’ll have to watch that evolution from afar. The Rays couldn’t afford to wait any longer for him to regain the value that he had lost. A trade made sense, while 2015 is still fresh in everyone’s minds.

Contact Thomas Bassinger at [email protected]. Follow @tometrics.