The Minnesota Twins needed pitching. The Miami Marlins needed hitting.

It was a match made in heaven when the Twins shipped former AL batting champion Luis Arráez to the Marlins in exchange for a pitcher with a solid floor and, as it turned out, some untapped potential: Pablo López.

López, who owned a 3.94 career ERA heading into this season, was universally seen as a solid mid-rotation starter in Miami but not quite an ace. He wanted more, though.

A smart man who knows four languages, López is also good with analytics. He tinkered with mechanics and new pitches in the offseason and decided he needed to come up with a pitch with a pronounced glove-side break. His changeup and two-seamer already gave him two solid arm-side break alternatives (particularly the former).

After a spring training outing, the world was put on notice. Asked about his repertoire and his breaking pitches, he told the Minnesota Star-Tribune:

“One was a curveball, and then (one was) — a ‘sweeper’ is the term I’ve been hearing a lot. I’m just trying to work on spin that goes north-south, and then a little spin that goes east-west. I want (them) spinning different to have more options.”

When talent meets hard work, good things happen. López is now throwing both variations of the curveball, the regular one and the sweeper – more like a ‘gyro’ or horizontal slider, with less downward movement than a slurvy pitch.

Pablo Lopez 2022 Movement chart
Pablo Lopez 2023 Movement chart

So the right-hander has basically taken the curve and shifted the spin axis up about 45-60 degrees while also ditching his cutter, which had been part of his repertoire for a long time. It’s fair to say that the results have been positive.

Over 26 innings in his four starts so far, López has a microscopic 1.73 ERA, a 2.78 FIP and an 0.81 WHIP. His 6/33 walk-to-strikeout ratio is also ridiculously good. And he’s limiting opposing hitters to a .490 OPS.

The changeup remains his best pitch, but the sweeper gives him an excellent option with glove-side movement to neutralize righties more effectively. By throwing it down and away with two strikes, he has yet another strikeout weapon.

Of course, the effectiveness of the sweeper, the changeup, the two-seamer and the more traditional curve has been aided by another promising development: López is throwing his four-seamer two miles per hour harder than he did in 2022.

He averaged 93.5 mph with it last year and is at 95.5 mph early on this season. The added velocity has an incredible effect on every pitch in the arsenal.

López was basically a two-pitch hurler last year, throwing 38.7% of four-seam fastballs and 35.2% of changeups, sprinkling in his two-seamer, curveball and a cutter each at less than 10%.

As a result of the increased velocity and the new sweeper, he overhauled his pitch mix. The four-seamer is still his favorite (33.4%) but the sweeper is now the second pitch in his repertoire at 23.0%. The change checks in at 19.8% and the two-seamer is at 15.8%.

He is now a four-pitch ace who adds in a traditional, north-south curveball every now and then (8.0%) to keep batters on their toes.

Pablo Lopez's 2022 arsenal with the Marlins
Pablo Lopez 2023 pitch types

Advanced stats agree with López’s breakout. By using raw value (RV), we can analyze a pitcher’s performance on a per-pitch basis rather than just the outcome of the at-bat. Plate discipline, bat-missing ability, command, contact management and other useful things are analyzed with this all-inclusive metric.

There are two types of raw value: total raw value, a cumulative stat, and RV-, a rate stat that examines performance relative to the league average of 100. López ranks seventh in MLB in both total raw value (minus-6.2) and RV- (47.3). In both cases, lower is better.

Just last year, López finished with a 106 RV- (below the league average). His growth has been considerable and can also be explained by his improvement in the three phases of pitching: bat-missing ability (whiff+), achieving what he wants with the ball (command+) and getting strikes (strike+).

His whiff+ has gone from 116 in 2022 to an impressive 147 this year, good for sixth in the league among qualified starters. This has aided his 116 strike+, which ended up at 106 last year. He is currently boasting the seventh-best mark in the league in strike+.

He always has had good command: it was 109 last year and is at 111 in 2023. The fact he is throwing 2.0 mph harder, added a new pitch and still has above-average command is really remarkable. If you were wondering about how the new sweeper rates using these advanced stats, it has been elite with a 23 RV-, 140 strike+ and a 158 whiff+.

Filthy stuff.

The bottom line is that by adding a sweeper, López now has a weapon for every situation and for batters of both hands. He seems more mature, he has four pitches he can trust, and he is throwing harder than ever.

The Twins had to surrender a talented contact hitter in Arráez, but to say the Twins have been happy with the trade would be an understatement. The rotation currently owns a 2.58 ERA and ranks first in starting pitching RV with López, Sonny Gray, Joe Ryan, Kenta Maeda and Tyler Mahle.

That’s certainly in large part thanks to the emergence of López. He appears to have earned frontline starter status, and that has to be one of the most surprising developments of the young season so far.

Greg Gifford contributed.