In 1990, Rickey Henderson came to the plate in the leadoff spot 588 times (out of 594 total plate appearances). He hit 28 homers out of that slot, walking 95 times and striking out just 60, en route to a .326/.439/.579 line as Oakland’s No. 1 hitter. He also stole 65 bases and was caught on just 10 attempts. All told, he produced a 10.2-WAR season that has since been eclipsed by only three position players: Barry Bonds, Cal Ripken, and Mike Trout.

Henderson’s 190 wRC+ mark in 1990 has been topped by a small handful of batters in the meantime, too: Bonds a bunch of times, Jeff Bagwell Mark McGwire. Bryce Harper did it last year, and Frank Thomas did, too, in the strike-shortened 1994 season. None of them provided such production out of the leadoff spot, however. By most criteria, it’s the greatest hitting season by a leadoff batter in history.

It will likely remain the greatest season by a leadoff batter after the 2016 campaign, as well. That said, Cardinals infielder Matt Carpenter is making a strong case for second-best.

In terms of pure value at the plate, Matt Carpenter is off to a great start. Carpenter’s .300/.419/.585 line has led to a .419 wOBA and a 167 wRC+ that leads the National League and is behind only David Ortiz in all of major-league baseball*. Over the last 365 days, Carpenter’s 154 wRC+ mark sits behind only Ortiz, Trout, Josh Donaldson, Harper, and Joey Votto, and his .277 ISO is the seventh best in baseball. Continued production at that level would give him one of the greatest-hitting leadoff seasons of all time.

*Numbers current as of Monday afternoon.

Before going way back to consider Carpenter’s place relative to all baseball history, let’s take a look at some more recent seasons first. From 2002 to 2016, here are the best wRC+ figures by a hitter with a full season (502 PA) occupying the top spot in the lineup, with Carpenter’s season up to this point included.

Highest wRC+ From Leadoff Spot: 2002-2016 Season PA wRC+ Matt Carpenter 2016 298 172 Mike Trout 2012 639 167 Shin-Soo Choo 2013 669 158 Hanley Ramirez 2007 526 157 Jacoby Ellsbury 2011 689 152 Hanley Ramirez 2008 622 149 Matt Carpenter 2013 632 148 Jose Reyes 2011 584 142 Alfonso Soriano 2006 610 141 Curtis Granderson 2007 628 139

Topping Mike Trout on a list is probably a pretty good indication that Carpenter is doing something with little precedent. Of course, he’s unlikely to keep up this pace. If he hits his more moderate projection of 132 wRC+ the rest of the way, he still ends up with a wRC+ right around 150, and one of the better seasons of the last decade, right in line with his own 2013 season.

Carpenter had an unusual 2015 season, first sidelined for exhaustion early in the year and then, after a period of offensive success, moved out of the leadoff spot. He struggled, and while it would be pure speculation to say that his struggles were due to moving in the order as opposed to lingering effects of the exhaustion or just random noise, that his period of struggles last season occurred outside of the leadoff spot caused his splits from the leadoff spot since the beginning of last year to appear pretty incredible.

In 653 plate appearances in the leadoff spot since the beginning of 2015, Matt Carpenter has recorded a 175 wRC+. From that spot in the order (min. 200 PA), Jose Altuve is second with a 138 wRC+. And just those two names together bring us to an interesting paradox: hitters who put up very good numbers tend to hit for power, and hitters who tend to hit for power are often moved out of the leadoff spot to create more opportunities with runners on base.

Take Altuve as an example. Altuve has produced a 165 wRC+ in a little over 200 plate appearances this season, but after his power surge, he has been moved to second or third in the lineup. The same happened to Brady Anderson during his 1996 season where 30% of his PA and 15 of his 50 home runs were somewhere other than leadoff. The Cardinals have briefly experimented with others at leadoff, but they have no high-OBP, low-power guys who might make sense in that spot.

To see where Carpenter’s season — as well as the seasons of Trout and Henderson — might rank historically, I consulted Baseball-Reference’s Play Index, with leadoff splits going back to the 1913 season. I initially sorted by OPS, and took the top 300 seasons, still requiring 500 PA from the leadoff spot. While OPS is useful, wOBA is better, so using Jeff Zimmerman’s basic wOBA calculation, I generated a wOBA for those 300 seasons. This is the top 20 (21 with Carpenter), with their OPSs listed, as well.

If Matt Carpenter reached the 502-PA threshold with the same OPS he’s recorded to date, it would represent the highest leadoff split in history. (Although Rickey Henderson’s wOBA is still ahead of his.) Comparing by eras is difficult and with different run-scoring environments and parks, wOBA doesn’t completely do the job. To help, the table below takes the top 30 seasons by wOBA (going down to .390 — nobody has ever had a wRC+ above 160 with a wOBA below .390, and just a couple dozen have even cracked 150), and looks at their complete seasons, which can include non-leadoff plate appearances.

The chart below is sortable and includes Basic wOBA, wRC+, baserunning runs (prior to 2002, this includes only steals and caught stealing) and offensive runs above average.

Greatest Leadoff Seasons of All Time Player Year Basic wOBA wRC+ BsR OFF Rickey Henderson 1990 0.435 190 8.8 69.4 Matt Carpenter 2016 0.422 167 -1.6 23.7 Mike Trout 2012 0.412 167 14.1 64.2 Rickey Henderson 1985 0.407 159 11.7 58.3 Pete Rose 1969 0.408 154 -2.0 42.7 Rickey Henderson 1993 0.403 151 7.5 46.0 Don Buford 1971 0.392 151 0.6 31.6 Jacoby Ellsbury 2011 0.397 150 5.1 47.5 Shin-Soo Choo 2013 0.402 150 2.6 42.8 Craig Biggio 1997 0.402 148 5.2 50.3 Richie Ashburn 1955 0.407 147 -0.9 36.9 Tommy Harper 1970 0.391 146 1.5 39.4 Craig Biggio 1998 0.395 145 6.5 48.9 Chuck Knoblauch 1996 0.422 145 2.5 46.3 Bobby Bonds 1973 0.390 145 2.3 40.7 Earle Combs 1930 0.409 145 -1.8 37.8 Eddie Yost 1959 0.390 145 1.4 37.6 Hanley Ramirez 2008 0.411 144 6.3 44.8 Hanley Ramirez 2007 0.424 144 3.7 43.8 Ray Blades 1925 0.404 144 -1.0 30.9 Lenny Dykstra 1993 0.397 143 2.6 44.1 Kenny Lofton 1994 0.407 142 6.7 36.0 Earle Combs 1927 0.398 141 -0.2 39.5 Eddie Stanky 1950 0.394 141 1.5 38.2 Darin Erstad 2000 0.410 140 2.0 42.2 Al Smith 1955 0.392 140 0.5 35.9 Kirby Puckett 1986 0.398 140 -0.9 34.4 Chuck Knoblauch 1995 0.400 139 1.1 33.1 Brian Downing 1987 0.404 139 -1.5 32.9 Curtis Granderson 2007 0.392 136 9.9 40.0 Eddie Joost 1949 0.392 136 -0.2 31.9 Harry Hooper 1920 0.391 136 -1.7 27.8 Earle Combs 1929 0.393 133 -1.4 29.0 Brady Anderson 1999 0.391 130 4.0 31.9 Alfonso Soriano 2006 0.404 129 3.9 31.8 Alfonso Soriano 2007 0.391 122 2.2 20.0 Johnny Frederick 1930 0.404 117 0.1 18.2

A couple things to keep in mind when looking at Rickey Henderson’s season:

He accomplished all of this in just 134 games and 594 PA.

His run number includes only steals and does not include runs on double plays or baserunning on balls in play, which would likely inflate his OFF total even more.

When we use wRC+, some of the seasons lose a bit of their luster. These aren’t necessarily the 30 best leadoff seasons, especially near the bottom, but it is likely we captured the very best seasons at the top. If Carpenter hits his projections, he’s likely to fall in the 7-10 range in terms of wRC+ — around the 150 mark — and in the middle of that list of OFF at around 38 runs above average. If he were to keep his current numbers up for the remainder of the season, he’d sit right there with Mike Trout in wRC+ and at around 50 runs above average. He would find himself right behind Henderson and Trout and even with Craig Biggio for one of the single-greatest offensive seasons of all time by a leadoff batter.