The Cubs’ offense was resurgent in May

By quite a few measures the Cubs have had the best offense in the National League in 2018. Don’t just take my word for it, take a look at the National League team batting leaderboard as of June 1:

This was built on the team really taking it up to another level in May as you can see below. I cross-referenced these offensive numbers with BABIP (batting average on balls in play) to see if they are the result of luck. A BABIP substantially over .300 would indicate an outlier, while BABIPs closer to .300 would be closer to average. While the team BABIP of .312 indicates the Cubs may be getting a bit lucky, that .312 BABIP is more sustainable than the .321 the Brewers are sporting and substantially less lucky than the .357 the Giants put up in May.

As you can see the Cubs are putting up impressive numbers across the board. They accumulated 2.6 more fWAR than the second best team (the Brewers) in May. They are back to leading the NL in BB% (despite Javier Baez’s insistence on swinging “as long as the pitcher is throwing.”) They are also at the top of the leaderboard in OBP, SLG, and wOBA. For the purpose of today’s article, however. I wanted to take a look at one particular stat: weighted runs created plus (wRC+) where the Cubs are dominating the team and individual leaderboards.

What is wRC+?

First a reminder of what wRC+ is and why it’s helpful. wRC+ uses wOBA (weighted on base average) to look at the runs created by a player or team. It’s adjusted for park effects. One of the things that is nice about wRC+ is that 100 is set as the average and any point above or below 100 indicates that a player is 1 percent above or below league average. In other words, the Cubs’ team wRC+ of 120 in May is 20 percent better than a team composed of league average players. It’s also an 18 percent improvement over the wRC+ of 102 they put up in March and April.

That’s a big jump in the month of May and as you can imagine the Cubs needed quite a few of their players to step up in order to make that happen. Let’s take a look at who led the way for the Cubs in wRC+ in May.

Individual players

The Cubs have four of the top 30 qualified National League players by wRC+ in May. That is tied with the Giants for the most representatives of any individual team. Let’s take a look at the National League wRC+ leaderboard:

The Cubs are well represented in the above group. Anthony Rizzo is riding a hot streak and led the Cubs offense in May with a 155 wRC+. He’s followed by Kris Bryant at 142, Willson Contreras at 135 and Ben Zobrist at 122. However, as I was looking at these numbers it seemed like someone was missing, after all, Albert Almora Jr. has been excellent all month and it was odd that he’s not on this list.

Well, it turned out both Almora and Ian Happ just missed the qualified mark, so I ran the numbers again with a minimum of 80 plate appearances.

While this run of the data bumps Zobrist out of the top 30 (he’s 34th), both Happ and Almora make the cut and the Cubs are the only team with five players in the top 30. Interestingly, Happ has the second highest wRC+ on the team in May at 152, just behind Rizzo. Almora is 28th with a wRC+ of 133.

How much of this is luck?

Having five players with a wRC+ over 130 is outstanding. No other team in MLB had five players over 130. The Yankees and Indians were the next closest with four a piece. The potent Red Sox offense had three. So I had to take a look and see how much of what the Cubs accomplished in May was luck.

To do this I ran Cubs batting statistics for players with at last 80 plate appearances and looked at their numbers and their BABIP.

So how much of this was luck? Well, the answer is, not much. Almora’s .375 BABIP indicates he’s due for a regression. The same is likely true for Addison Russell’s who rode a .396 BABIP to a 111 wRC+ in May. Everyone else looks remarkably sustainable, although it wouldn’t shock me if Bryant or Happ cooled off a bit.

Two final takeaways from this data. First, Anthony Rizzo somehow built a 155 wRC+ on a .262 BABIP, which indicates he’s due for an improvement going forward, which would be incredible news for the Cubs in June.

Finally, it’s worth noting that the Cubs don’t have a single player with at least 80 plate appearances in May who had a wRC+ under 100. Every regular batter was above average in May.*

This bodes well for the Cubs offense as they enter June. The weather continues to get warmer in Chicago and I think there are good reasons to believe the Cubs bats aren’t cooling off any time soon.

* Since someone will ask: Jason Heyward didn’t quite make the cut for this table (he only had 58 plate appearances in May). However, it’s worth noting that his wRC+ of 90 in May is an improvement over each of his previous season marks with the Cubs. He’s also slashing .364/.405/.515 with a wRC+ of 147 since returning from the disabled list.