As we can see below, a hot start on the mound can come in all different shapes and sizes, with each of the following hurlers currently owning an ERA that is at least two full runs lower than what their SIERA suggests it should be.
| Rank | Player | K% | BB% | HR/9 | BABIP | LOB% | ERA | SIERA | Diff |
|---|---|---|---|---|---|---|---|---|---|
| 1 | Jeremy Hellickson | 9.6% | 2.6% | 0.60 | .196 | 86.2% | 1.80 | 5.36 | -3.56 |
| 2 | Ervin Santana | 21.1% | 8.1% | 0.51 | .129 | 99.0% | 0.77 | 4.19 | -3.42 |
| 3 | Gio Gonzalez | 19.4% | 8.2% | 0.81 | .258 | 89.1% | 1.62 | 4.31 | -2.69 |
| 4 | Dylan Bundy | 18.9% | 4.9% | 0.55 | .264 | 89.0% | 1.65 | 4.22 | -2.57 |
| 5 | Derek Holland | 18.9% | 9.0% | 0.93 | .229 | 71.4% | 2.17 | 4.65 | -2.48 |
| 6 | Blake Snell | 15.5% | 15.5% | 1.03 | .234 | 66.1% | 3.42 | 5.90 | -2.48 |
| 7 | Cole Hamels | 11.5% | 9.2% | 1.10 | .219 | 79.1% | 3.03 | 5.36 | -2.33 |
| 8 | Mike Foltynewicz | 19.2% | 9.1% | 0.76 | .250 | 76.3% | 2.28 | 4.45 | -2.17 |
| 9 | Chase Anderson | 20.0% | 7.5% | 0.30 | .259 | 76.0% | 2.10 | 4.23 | -2.13 |
| 10 | Ian Kennedy | 23.1% | 11.6% | 0.86 | .184 | 85.8% | 2.30 | 4.42 | -2.12 |
| 11 | Dallas Keuchel | 21.8% | 6.7% | 0.81 | .186 | 98.7% | 1.21 | 3.32 | -2.11 |
| 12 | Ivan Nova | 16.5% | 0.8% | 0.50 | .224 | 79.4% | 1.50 | 3.60 | -2.10 |
| 13 | Mike Leake | 19.1% | 3.8% | 0.00 | .277 | 84.9% | 1.35 | 3.41 | -2.06 |
| 14 | Jameson Taillon | 19.2% | 9.6% | 0.59 | .279 | 85.6% | 2.08 | 4.13 | -2.05 |
| 15 | Matt Cain | 19.5% | 8.0% | 0.99 | .253 | 89.9% | 2.30 | 4.33 | -2.03 |
This doesn't necessarily mean each of them would be off to a terrible start if everything wasn't going their way, though. There are still three on this list -- Dallas Keuchel, Ivan Nova and Mike Leake -- who have a sub-4.00 SIERA.
However, it shouldn't be surprising to see Philadelphia Phillies right-hander Jeremy Hellickson at the top. Outside of having a sub-.200 BABIP, the most concerning part of his stat line includes that 9.6% strikeout rate. His career 17.8% mark tells us he's never been much of a strikeout pitcher, but it's a stark contrast from the career-high 20.0% mark he produced in 2016.
If you're looking for things to feel encouraged about, avoid his 8.1% swinging-strike rate, which would be under 10.0% for the first time since 2013 if he sustained this pace for the remainder of the year.
Ervin Santana is in a similar boat -- he's been tremendous, but he's been aided by producing the lowest BABIP (.129) and highest strand rate (99.0%) of the above group. When things start to normalize, how much different will his performance look?
If you're on the hunt for pitching, looking at advanced stats such as these should help temper expectations for certain pitchers moving forward, while also allowing you to avoid overpaying on the trade market.