Confirmation Biases and Cliff

When an otherwise average player suddenly puts up one of the best seasons of the decade, fans are not only going to take notice, but they will also be very skeptical that the performance can continue. The kneejerk reaction is to suggest regression to the mean in the coming season(s), especially if the solid numbers were more contingent upon luck based indicators than the controllable skills that tend to stabilize quickly. In the case of Cliff Lee, the bandwagon of fans suggesting he would stink this year grew as vast as the group that swore last season was “for real.”

Even though Lee’s strikeout, walk, and groundball rates were more responsible for his turnaround, the majority of fans felt he would come nowhere near a repeat performance this season. When Lee’s first two starts ended with 17 hits and 11 earned runs in just ten innings of action, confirmation biases reigned supreme.

A confirmation bias is essentially what happens when someone actively seeks evidence to confirm what they think is true. With regards to Lee, someone who felt he would significantly regress would view these two game lines and proclaim that the Cliffer had finally gone back to his old ways.

Well, eight starts into the season, Lee’s line looks like this: 8 GS, 54 IP, 3.00 ERA, 3.17 FIP, 7.0 K/9, 2.2 BB/9. His 1.41 WHIP is not likely to stay as high nor is the 81% strand rate that has virtually canceled out the walks and hits ratio. Lee has already produced +1.7 wins in spite of two poor outings to start the season.

Since his second start, Lee has gone 44 innings while surrendering just seven earned runs. He has a tidy 4.0 K/BB thanks to 32 punchouts and eight free passes. Even though Lee got off to a rough start, he has rebounded very nicely to the tune of a 1.43 ERA and 2.78 FIP over his last six starts. With the dominating season turned in last year and his stellar performance so far, ZiPS sees Lee finishing this campaign with a 3.43 FIP in 208 innings. Numbers like that resemble John Danks‘ line from 2008, which produced +5.2 wins.

Cliff Lee might never again surpass the +7 win plateau but his current pace will still likely merit some award votes and a spot on the all star team. He does not have the pedigree or reputation of a Halladay that would instill supreme confidence into the minds of fans, but Lee has, through eight starts, done plenty to show that last season was not a fluke.

We hoped you liked reading Confirmation Biases and Cliff by Eric Seidman!

Please support FanGraphs by becoming a member. We publish thousands of articles a year, host multiple podcasts, and have an ever growing database of baseball stats.

FanGraphs does not have a paywall. With your membership, we can continue to offer the content you've come to rely on and add to our unique baseball coverage.

Support FanGraphs

Eric is an accountant and statistical analyst from Philadelphia. He also covers the Phillies at Phillies Nation and can be found here on Twitter.

newest oldest most voted

Just because he didn’t fall off a cliff(heh) this year, doesn’t mean last year wasn’t a fluke. Going from +7 -> +5.2 win’s is pretty much a fluke. Of course, just because last season was a fluke, doesn’t mean he will suck this year. It just means he will be a good, rather than great pitcher. If a good player has a great year and then goes back to being good, it’s still a fluke. I don’t think confirmation bias is what you want here. It’s probably a form of anchoring again.


Only Lee’s not taking the good —> great —> good route. You couldn’t fluke your way from replacement level to Cy Young in one year’s time with all the luck in the world. Average —> excellent —> slightly less excellent is more like it.