When Guerra was fully healthy in 2016, he averaged over 6 IP per start. He's the rotation wild card just as he was then. Now everyone has Woodruff in the rotation and there's no doubt he'll start the year there, but he's got an option, so if 6-8 starts in he's struggling, he could find himself back in Colorado Springs in a worst case scenario. There's always the potential for injury or having whoever wins the 5th spot struggle too. Having Suter and Guerra start the year in the pen, and assuming they get fully stretched out in Arizona would allow Counsell to insert either one of them in that spot if need be early on. As the season goes on, and the benefit of the spring stretch-out wanes, if a rotation spot opens up, I think then we could see a piggy-back arrangement at least for a few starts involving those two.