Over the last two seasons, Zach Eflin has a 4.23 ERA and Jake Arrieta has a 4.26, each of them between 1-2% better than the league average in that span.
The 2020 Phillies need at least one to pitch his way closer to the 3.50 to 3.75 range in 2020.
Eflin had a decent season in '19, going 10-13 with a 4.13 ERA in 163⅓ innings. His strikeout rate dropped from a one-year spike of 8.7 per nine innings to 7.1 but some of that was owed to his departure from what had become the philosophical norm for Phillies pitchers: throwing four-seam fastballs up in the zone. Eflin went back to throwing his sinker and trying to keep the ball low and it worked for him late in the season as he got back on track.
It's good that there is again more conviction in Eflin's pitches. But it remains to be seen whether he can be successful over a full season with his pitch-to-contact approach. He's been sharp and efficient in bursts but never for prolonged periods. Three or four really good starts in a row, then a four-inning, six-run start filled with hard contact.
There is sufficient evidence to suggest Eflin has a place in a big-league rotation. He had two complete games as a rookie in 2016 and two more last season in a year when nobody else in the NL had more. That's not just a random factoid but an example of how much he can control a game when he is hitting spots and working quickly. He has pitched at least six innings and allowed two earned runs or fewer in nearly 40% of his career starts.
The projection systems, though, don't love Eflin because they tend to favor pitchers who miss more bats and he's just not a high-strikeout guy. His walk rate is better than average but his career home run rate is slightly below.
Two of the most common public projection systems for baseball players are Steamer and ZiPS. Steamer projects a 5.04 ERA for Eflin in 2020; ZiPS has him at 4.64. Baseball-Reference's model has him at 4.41.
Any of those three marks would be a disappointment. For the Phillies to take a step forward in 2020 they will need Eflin and Arrieta to pitch more like No. 3s than No. 5s. Especially with so much uncertainty in the bullpen.
Eflin did take a positive step in 2019. His ERAs by month were 3.34, 2.64, 4.02, 11.88, 3.77 and 2.80. Had his July been even normal-bad as opposed to horrid, there would be a lot more buzz around the 26-year-old right-hander.