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The Philadelphia Phillies, with their latest victory on Monday night against the Cincinnati Reds, are now riding a seven-game winning streak. The Phillies have scored seven runs or more in each of their last five contests, making it easy to miss just how dominant their rotation has been -- both, during this stretch and overall this season.

Put another way, the Phillies have received at least a quality start in each of those seven victories. In six of them, their starter has worked at least seven innings and has surrendered two runs or fewer. Only once in their last 14 games has their starter allowed more than three runs in a contest. It is any wonder why they're 11-3 over that span?

And is it any wonder why the Phillies rotation leads Major League Baseball in several notable categories? It's tough to do much better than this:

  • ERA: 2nd
  • IP: 1st
  • K/9: 5th
  • GB%: 1st
  • FIP: 2nd

With that in mind, below we've presented a thing worth knowing about each member of the Phillies rotation: Zack Wheeler, Aaron Nola, Ranger Suárez, Cristopher Sánchez, and Spencer Turnbull. In some cases it's an interesting statistic, in others it's an observation about a tweak they've made. We hope that this helps you gain an appreciation for what could be argued is presently MLB's best performing rotation.

1. Wheeler has a new toy

Back in March, our weekly roundtable prompt responded to the news cycle by asking: "who's the best active MLB pitcher now that Gerrit Cole is hurt?" 

This author, as luck would have it, chose Zack Wheeler. Here was part of the reasoning: "He leads MLB in pitching Wins Above Replacement (FanGraphs' version) while possessing a slightly better ERA than Cole over the last three seasons. (He's also been dominant in the postseason the last two falls, meaning his regular-season numbers alone understate his brilliance and his importance to the Phillies.)"

You don't have to agree with the idea of Wheeler being the best active pitcher to acknowledge that he's been a high-level performer since joining the Phillies. He's compiled a 140 ERA+ over 106 starts to date, and even now, it seems laughable that he's only managed to make one All-Star Game appearance. Anyway, here's a scary thought: he may have added another quality weapon to his repertoire in a splitter.

Wheeler has deployed the splitter as his most-used non-fastball to date, chucking it to great effect. Opponents are hitting .118 on it, and that's when they make contact. The splitter's 37.1% whiff rate is second best in his arsenal, behind only his sweeper. Wheeler explained how he came to trust his splitter during a March radio appearance.

"I've kind of always switched around between a traditional changeup and a split," he told 94WIP's Midday Show with Hugh Douglas and Joe Giglio. "I've probably threw it like five times a year the past few years and that's to like Freddie Freeman in like a 3-2 count, please swing at it. This year I've made a concerted effort to really work at it. Literally sit on the couch throughout the offseason, play around with some grips. Caleb [Cotham], our pitching coach, is really awesome at hand manipulation with the ball and he's made my offspeed pitches a lot better and he's helped me out with the split."

The early results are so promising that, who knows, maybe Wheeler will claim the title of best active pitcher by winning the National League's Cy Young Award.

2. Suárez has set the pace

Ranger Suárez doesn't get the same amount of press as his more famous teammates. So far, though, he's been the one establishing the standard for the Phillies rotation. 

Through five starts, Suárez has amassed a 1.36 ERA (306 ERA+) and a 6.40 strikeout-to-walk ratio. He's allowed just 18 hits and five walks in 33 innings. What's more is that he hasn't surrendered a run in his last 25 innings. That's the longest scoreless streak of the season, according to Baseball Reference's database. 

Suárez also leads qualified starting pitchers in ground-ball percentage. He's stayed true to himself in that and other respects: he remains a sinkerballer who mixes and matches between his four other offerings (a curveball, four-seamer, changeup, and cutter that he throws exclusively in the kitchen to right-handed batters).

Not everyone has to be Wheeler, experimenting with an already successful formula. Oftentimes, it's good enough to keep doing what works. In Suárez's case, that philosophy is working really well.

3. Nola succeeding despite some question marks

One of the difficulties of April analysis is juggling the descriptive and the predictive, between writing what has happened and prognosticating on what may happen based on the whole picture. The reality is that small sample sizes often result in misleading appearances. In many cases, they outright mask potential red flags.

Nola, we regret to assert, is a good example of that dynamic at play.

From a surface-level perspective, Nola has been fantastic. In five starts, he's accumulated a 3.16 ERA (132 ERA+) and a 2.60 strikeout-to-walk ratio. He's even averaged more than six innings per pop. Take a deeper dive, however, and there's reason to wonder about how the rest of his season will play out.

To wit, Nola's velocity is down nearly two ticks: from 92.7 mph last year to 91 mph this year. To be fair, that number is skewed by an outing amid unfavorable conditions in St. Louis. Take that start away and the gap isn't as large (though he's yet to average higher than 92.1 in a start).  

What's more is that, while racking up empty swings hasn't been his forte, his 48th percentile rank in swinging strikes in 2023 would represent a vast improvement over where he places so far this season. Indeed, his whiff rate on his fastball and his changeup have cratered, resulting in a would-be career worst rate of 19.9%. This would represent the fourth-worst monthly mark of his career, and the lowest since April 2018.  For context, Nola ranks 80th in whiff rate among the 106 pitchers with at least 20 frames. That's not an ideal development for someone at the onset of a seven-year pact.

Granted, it's very early in the season. Nola has a long history of being a good pitcher. He may be able to adjust and reintroduce some swing-and-miss capacity to his game. He may even find a way to succeed without doing that. We just mentioned April 2018 -- he went on to finish third in Cy Young Award voting that year. Maybe he pulls off a similar trick this season. At this point in time, we have no way of knowing for sure. 

4. Sánchez has changed perception on trade

A running joke on the baseball internet holds that the Tampa Bay Rays are almost always declared the winners of their latest trade -- to the extent that the exact details hardly matter. That collective reflex has been learned for a reason: the Rays do "win" a lot of their trades. For a time there, it appeared that they had snookered the Phillies as part of the November 2019 trade that swapped Curtis Mead and Cristopher Sánchez.

Mead was a young corner infielder whose bat would soon land him favorable rankings on prospect lists. Sánchez was a left-hander who had spent a considerable amount of his career in a relief role. Through, let's say … the 2022 season, the Rays appeared to have won the deal in a boat race. Mead looked like a future middle-of-the-order hitter, and Sánchez was sporting a 5.47 ERA through his age-25 campaign.

Since then? The trade narrative has done a 180-degree turn. Mead, while still young and promising, hasn't taken to big-league duty quite as well as anticipated. (He has a 79 OPS+ through his first 43 games in the majors.) Sánchez, meanwhile, has turned into a legitimate big-league starter. Dating back to last season, he's posted a 130 ERA+ and a 5.04 strikeout-to-walk ratio in his last 23 appearances (22 of them starts).

If you're unfamiliar with Sánchez's game -- and, to be fair, he's thrown all of 2 1/3 postseason innings -- he's a bit of a throwback. He has three offerings: a low-90s sinker and a screwball-like changeup that both feature ample arm-side run, as well as a slider that keeps batters honest with respect to pitch movement. Sánchez gets his fair share of strikeouts, but he's especially skilled at generating wormkillers. His 62.7% ground-ball percentage would lead the majors' starting pitcher crop if he qualified.

5. Turnbull also has a new pitch

A reasonable reaction to the Phillies signing Spencer Turnbull in February was to have no reaction at all. He was coming off a miserable, multi-year stretch that included a prolonged absence caused by Tommy John surgery. Turnbull did return to the majors last season, but was limited to seven outings (and a 7.26 ERA) before being banished to the minors from August onward.

Yet Turnbull has thus far looked the part of a nifty addition by the Phillies. In his first four starts, he's compiled a 1.23 ERA and a 3.14 strikeout-to-walk ratio. He's unlikely to keep up this pace, but there is some reason to think he's improved compared to his recent past self -- and that's largely because of a new pitch. 

Turnbull hasn't just added a sweeper to his arsenal, he's fully embraced it. To date, he's thrown it the second most frequently of any of his pitches, behind only his four-seam fastball. Both of those offerings have been thrown more than 100 times; he hasn't used any other pitch more than 40 times. Turnbull's sweeper, in turn, has been a revolution for him. It has a 32.5% whiff rate and has held opponents to a .091 average.

Baseball Prospectus has a metric called "StuffPro" that uses a pitch's characteristics -- velocity, movement, spin profile, and so on -- to determine its quality. Turnbull's sweeper grades as the 27th best pitch among the 244 thrown at least 100 times this season. It ranks 12th among breaking balls. Adding a pitch of that quality is a quick way to turn a fairly nondescript addition into someone worth monitoring. Not bad for someone who probably wouldn't be in the rotation were it not for an injury to Taijuan Walker.