FanPost

Advanced Stats Explained: OPS+

I'd like to start my first post with a hot take: the San Francisco Giants have not been fun to watch this season. Even if you haven't watched a single game or paid attention to the standings this would be evident from some of the latest McCovey Chronicles headlines - "What Do the Giants Have to Play For?"; "Giants Lose By a Bunch Again"; "The Giants Have the Worst Run Differential in the National League"; "Giants Receive Permission From MLB to Explore Two-City Solution with Montreal". OK, so things could be worse, but my point is that I'm not the only one who's having a hard time convincing themselves it's a good idea to spend 3 hours of their day hoping for something resembling decent baseball to occur.

While I've enjoyed following the progress of some of the minor league prospects like Joey Bart, Heliot Ramos and Sean Hjelle, I've been looking for other ways to be entertained as the Giants slowly begin the rebuilding process. Advanced stats are something I have at least some familiarity with but haven't taken the time to understand how they're calculated or why they're more helpful than traditional stats. So with that let's dive into the world of On-Base Plus Slugging Plus (OPS+).

What You Need to Know First

If you're not familiar with OPS (On Base Plus Slugging) keep reading, otherwise skip down to the next section. Here's the definition from the official MLB website:

OPS adds on-base percentage and slugging percentage to get one number that unites the two. It's meant to combine how well a hitter can reach base, with how well he can hit for average and for power.

Let's break it down even more. On-Base Percentage (OBP) is how often a player reaches base no matter how they get there (hit, walk or hit by pitch) divided by their plate appearances. We'll use a current Giants player to illustrate how to calculate this, but we'll use his stats from a previous season since that is less likely to make us sad. I'll call him Player A (hint: this is from an all-star season):

Player A - Hits: 149; Walks: 104; Hit-By-Pitch: 5; Total Plate Appearances: 655

So we add hits, walks and hit-by-pitch together (149 +104 + 5 = 258) and divide that by the total plate appearances (655)

258/655 = .394 On-Base Percentage (OBP)

Slugging Percentage (SLP) is the total number of bases reached per at-bat. This adds up all of the singles, doubles, triples and home runs and divides it by the number of at-bats (NOT plate appearances, as that includes walks and hit-by-pitches). However, the value of the hits increases exponentially - the number of doubles gets multiplied by 2, triples by 3 and home runs by 4. How did our anonymous Giant do in his all-star year?

Player A - Singles: 83; Doubles: 41; Triples: 8; Home Runs: 17; At-Bats: 542

[83 + (41 x 2) + (8 x 3) + (17 x 4)]/542 = (83 + 82 + 24 + 68)/542 = 257/542 = .474 Slugging Average (SLG)

Now all we do is add our final numbers together:

.394 OBP + .474 SLG = .868 On-Base Plus Slugging (OPS)

Let's Do This

So what does the + add to OPS? Once again here's the definition from the official MLB website:

OPS+ takes a player's on-base plus slugging percentage and normalizes the number across the entire league. It accounts for external factors like ballparks. It then adjusts so a score of 100 is league average, and 150 is 50 percent better than the league average.

We're already masters of calculating OPS so all we need to do now is figure out how to determine park adjustments. How difficult could that be?

This is the very first sentence from the Baseball-Reference page regarding park adjustments:

These numbers are difficult to calculate and I would refer you to a copy of Total Baseball if you wish to recreate the park factor values.

You don't scare me nerds! I'm just going to keep reading this page and...

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Let's keep it simple: OPS+ seeks to minimize outside factors such as the advantages and disadvantages of playing at certain ballparks to get a better idea of how a player is truly performing at the plate. This would generally make Giants hitters look better than their OPS and other traditional stats since Oracle Park is not known as being hitter friendly.

After all the math magic happens the league average is 100, so anything greater than that is an above-average player and anything lower is a below-average player. Here are Player A's final stats on the season:

Player A - OPS: .868; OPS+: 135

In the year Player A put up these numbers the league average for OPS was .739, with the top team sporting .810. The league average for OPS+ was 97 and the top team had 112.

So Player A was definitely a good batter, but just how good was he? Out of 21 batters for the NL All-Star team only 7 had a higher OPS on the season. Add that little plus sign on the end and it drops to 4 players.

Summary

Like most traditional stats, OPS gives you an idea of how well a player is performing. OPS+ strips away the outside advantages and disadvantages like ballparks and gives us a truer sense of how a player is doing offensively. Until the fences are moved in and Triples Alley turned into a bullpen I recommend paying more attention to OPS+ to understand how well Giants players are doing on offense.

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