The Pirates are the early surprise team of the 2023 season.

After completing sweeps of the Rockies and Reds last week to push their winning streak to seven games, the Pirates improved to 16-7, the third-best record in the Majors through Sunday. Both the wins and the vibes are contagious right now. The Bucs are off to an unexpectedly great start coming off a four-season stretch (2019-22) in which they won the fewest games (211) of any team, including just 62 a year ago.

While it¡¯s been a collective improvement from both the pitching and hitting, it¡¯s the latter that¡¯s been the main driving force for the Pirates' hot start. Given that they finished in the bottom five in both runs (591) and OPS (.655) in 2022, their placement in the top eight in both runs (111) and OPS (.765) in '23 represents a monumental step forward.

It¡¯s even more impressive that they¡¯ve done so without Oneil Cruz, one of their bright young stars who fractured his left ankle on April 10, and Ji-Man Choi, who owns a career 113 OPS+ and was just placed on the 60-day IL due to a left Achilles strain.

The question is how has the Pirates' offense gone from one of baseball¡¯s worst to one of baseball¡¯s best in such a short span?

Few offenses have had this kind of recent year-to-year improvement

It would be remiss to not include the caveat that it¡¯s still early in the season and small sample size noise applies.

That said, the Pirates haven¡¯t just improved on their 2022 offensive performance in a major way; they¡¯ve made one of the biggest year-to-year offensive jumps that we¡¯ve seen in the Statcast era (since '15).

When looking at expected wOBA -- or projected wOBA based on the quality of contact, strikeouts and walks -- the Pirates have made the third-largest year-to-year improvement in offensive performance.

Largest year-to-year team offense xwOBA improvement, since 2015
Rays, 2022-23: .298 to .366, 68 points
Padres, 2019-20: .299 to .357, 58 points
Pirates, 2022-23: .289 to .345, 56 points
Twins, 2018-19: .306 to .346, 40 points
Orioles, 2022-23: .310 to .339, 29 points

There are the 2023 Rays who, as you might have seen, are 20-3 and homered in a record 22 straight games to begin the year. There are the 2020 Padres, who, in the COVID-shortened season, drastically improved largely due to the first MVP-level performances from Manny Machado and Fernando Tatis Jr. Then you have the Pirates, who have had a whopping 56-point increase in xwOBA this season.

What¡¯s neat is all of the offensive numbers agree, whether you¡¯re looking at the traditional measures (runs, BA, SLG) or some of the underlying expected numbers (xwOBA, xBA, xSLG). They universally support the fact that the Pirates are performing on a completely different level this season.

Pirates¡¯ MLB rank, 2022 vs. ¡®23
Runs: 28th vs. 8th
xwOBA: 28th vs. T-5th
xBA: 29th vs. 7th
BA: 29th vs. tT-12th
xSLG: 29th vs. 5th
SLG: 27th vs. 6th

How the Pirates' offense has improved this much

What exactly has sparked this kind of across-the-board improvement for the Pirates' offense?

From an individual player perspective, it started last offseason when the club heavily invested in bringing in more proven MLB hitters during the winter. Names like Andrew McCutchen, Carlos Santana and Choi didn¡¯t garner headlines in a frantic and transactional winter, but they represented legitimate MLB hitters on a team desperate for some.

To their credit, McCutchen and Santana have both produced in roles as hitters and leaders in the Pirates' clubhouse. McCutchen has resurrected his vintage Bucs form by posting his best OPS+ (144) and xwOBA (.389) since 2015. Santana¡¯s 108 OPS+, meanwhile, is his best since '19.

It¡¯s not just the well-known veterans producing. Connor Joe, originally drafted by the Pirates in 2014, has been one of the best under-the-radar pickups and leads Bucs hitters with a 1.098 OPS. Jack Suwinski has a 1.021 OPS and is a top-5 qualified hitter in the Majors by xwOBA (.457). Bryan Reynolds has produced a 136 OPS+ and a .408 xwOBA that signals that more production could be coming. Even Rodolfo Castro, Cruz¡¯s replacement at shortstop, has a 119 OPS+ and a .338 xwOBA.

From a team-wide perspective, the club has moved in a positive direction both in terms of the quantity and quality of their contact.

Pirates¡¯ MLB rank, 2022 vs. ¡®23
Whiff%: 21st vs. 11th
Chase%: 10th vs. 3rd
Zone swing%: 30th vs. 9th
Hard-hit%: 19th vs. 4th
Exit Velocity: T-17th vs. 4th
Barrel%: T-22nd vs. T-6th
Meatball swing%: 28th vs. 1st

For the Pirates, a better approach at the plate has led to more hittable pitches on which to inflict damage. Of all improvements listed above, perhaps no stat is as telling as Pittsburgh's near-10% increase in meatball swing%. The Bucs haven¡¯t actually gotten more meatball (middle-middle) pitches to hit; they¡¯ve simply started swinging more at those hittable pitches.

In terms of the plate discipline improvement, the approach at the plate appears to be intentional. As Chris Gilligan recently covered at FanGraphs, many Pirates hitters are making better swing decisions. Hitters like Reynolds, Suwinski, Joe and Castro are chasing less and finding more hittable pitches in the middle of the zone.

Those better swing decisions have led to a higher quality of contact. As MLB.com¡¯s Manny Randhawa found last week, the Pirates had a game at Coors Field with 15 batted balls classified as hard-hit (95+ mph exit velocity). They had not done that before in a single game in the Statcast era (since 2015).

Up and down the roster, the Pirates are seeing huge offensive returns on both an individual player and a team-wide level.

Can this hold up?

Whether the Pirates' offensive performance is sustainable remains to be seen.

One would think that this current collection of hitters is unlikely to finish the season as a top-10 offense. Expecting the Pirates to continue to produce better offensive outcomes than teams like the Blue Jays, Mets and Astros might be a stretch.

The projection systems, too, are split on how to view the Pirates' offense for the rest of the season. Updated ZIPS and Steamer projections appear to be buying some of the individual player improvements, namely players like Joe and Suwinski. The BAT X, which incorporates Statcast data, is less convinced about the improvements and expects the collective group to fall back to earth.

What is certain, though, is we are having a conversation about how good the Pirates' offense and the overall team is. The fact that the club is off to a 16-7 start is a testament to the improvements across the board for the Bucs' offense and its individual players.

Now, it¡¯s a waiting game to see if this continues for the rest of the season and helps the Pirates get back to the playoffs for the first time since 2015.