Streaming Pitchers vs Opponents wRC+
Streaming pitchers is a long-standing fantasy baseball strategy. It is when you add a pitcher to your team based on the matchup, hoping that they provide solid ratios and over perform. A streamer is someone who you add for a short term and wouldn’t carry as a permanent member of your team. When it comes to strategy for streaming pitchers there are many different stats to consider. You can analyze the pitcher’s latest performance and look for velocity or an uptick in K-BB%. Or you can look into the opponent’s offense and their recent wOBA or wRC+. A lot of people don’t have the time to do that or prefer a simpler way. I decided to look at how streamers did against opponents who were in the bottom ten in wRC+ in the last 14 days prior to their start. For instance, if a streamer started on 5/14, I took their opponent and checked to see if they were bottom ten between 5/1-5/14 in wRC+. If they were then I counted the stats. So what is wRC+? wRC+ stands for weighted runs created plus. As Fangraphs explains it, “credits a hitter for the value of each outcome (single, double, etc) rather than treating all hits or times on base equally, while also controlling for park effects and the current run environment.” Basically, it is a much better indicator of average. If a team has a terrible wRC+ they aren’t hitting a lot of home runs, triples, or doubles. Which of course, bodes well for pitchers.
For my little study, I decided to take 15 streamers from 2019. All of them finished the season under 30% owned in Yahoo!. They range anywhere from 29% owned to as low as 2% owned. Overall the study looks at 704.2 innings worth of data as well as 122 starts. Below is a breakdown of each pitcher and what their ERA was for the year when they faced opponents who were bottom 10 in wRC+ at the time of the start.
Only three of these pitchers had a worse ERA when facing opponents in the bottom 10 in wRC+ 14 days prior to their start. This appears to be pretty useful and a viable way to stream pitchers quickly if you don’t have the time to do a lot of research. 7 of the 15 pitchers reduced their ERA to under four. 6 of the 15 pitchers had a reduction in ERA of over 1. To take this a step further I gathered all of their starts and put them together to see what the overall picture would look like.
The league’s ERA for 2019 was around 4.50. This was the highest league average in quite some time. The fact that you could get a 4.00 ERA by using this strategy is a pretty big advantage. The WHIP and K/9 aren’t too shabby either. If you told me coming into 2019 “stream pitchers against opponents who are bottom ten in the last 14 days and you will average a quality start,” I would be all in.
Fantasy players look at a lot of different stats when picking streamers. I think opponents in the bottom ten in wRC+ the last 14 days are a great go-to stat for quick decisions. If you want to see the breakdown of every pitchers start you can go here. I certainly will be looking at it when I make my streaming picks in 2020. As always thanks for reading and let me know if you have any questions!