Rays have a bunch of those type of arms: Austin Pruitt, Ryan Yarbrough, and Matt Andriese. They're No. 5 starters at best and maybe 6th, 7th starters on a contending teams depth chart and aren't good enough to make it through 30 + starts over a full season. Use them only for 3-4 innings starting from the second inning on and they likely have more success. As well, gives the Rays BP like you said more options in multi-inning relievers if you ever need to use them again within those 4-5 days. For example, I'm sure if Andriese gives you 3.1 innings on Saturday out of the pen, I'm sure you can use him again on Monday for Tuesday for 3-6 outs if you need to before you have him go again on the Thursday.