Is Sean Marshall the best reliever on the Cubs?

I know I’m not the first person to ask this question and with Carlos Marmol‘s recent meltdown, probably not even the first to ask it in the last few days. We can ignore the recent meltdown altogether and focus on the last two years instead. I chose the last two years because it’s quite clear Sean Marshall became a different pitcher over the last few years. His fastball velocity has jumped about 5 mph from what it was in 2008 and it has jumped 2 mph from what it was in 2009. As a result, Marshall’s strikeout rate has jumped considerably and he’s just a far better pitcher than he once was. This doesn’t mean we can expect his current performance to continue. We can’t. He’ll regress somewhat, but I’m not interested in that right now. I’m just wondering if Sean Marshall is or has been better. 

Over the last two seasons, batters have hit only .226/.284/.294 against Marshall. Against Marmol, batters have hit .182/.312/.251. Marshall’s OPS is a bit higher, but proper weighting makes them roughly equal to one another. 

Since 2010, Marshall has been worth 20.7 Pitching Runs according to Baseball Reference, 2.1 Pitching Wins, accrued 2.6 WPA, 20.4 RE24 and 2.0 REW. Marmol has been quite good, but he’s added just 15.7 Pitching Runs and 1.6 Pitching Wins. Thanks to pitching in higher leverage situations, Marmol has a higher WPA (3.2). He also has a higher RE24 and REW, but not by much at all. 

Marshall’s FIP is 2.15 while his ERA is 2.71 and his xFIP is 2.55. His fWAR is 4.3. Marmol’s FIP is 2.60 and his ERA is 3.20 while his xFIP is 3.30. His fWAR is 3.9. Over the last two seasons, Sean Marshall has been the superior pitcher and I’m not sure it’s that close. 

Marmol has allowed 11.6 baserunners per 9 innings while Marshall has allowed only 10.2 per 9. 

Even if we go back to 2009 and use relief innings only, Marshall has still been better. Marshall has a 2.83 ERA, 2.51 FIP, 2.78 xFIP and 4.8 fWAR. Marmol has a 3.27 ERA, 3.11 FIP, 3.92 xFIP and 4.5 fWAR. 

Going back to 2008 we find that Marmol has now thrown 100 more relief innings than Marshall, but Marshall’s ERA is 2.91, his FIP is 2.80 and his xFIP is 3.02. Marmol’s ERA is 3.10, his FIP is 3.26 and his xFIP is 3.85.