What do you do with a guy whose durability is 8?  His stamina is 65.  Seems like any time he pitches....no matter how few innings he works...he's out of commission for a week to ten days.  Is there a way to use this guy so he can pitch more often?  Or is he just useless?

Setup reliever.  Pitch count of 20/25 or so.  Don't let him pitch every day.

Make sure you set his minimum fatigue level at something like 98%+.  Otherwise he could end up with a lot of appearances in the low 90s.

This guy has been a pet project for me the last few seasons.  He has good stuff so he has been somewhat useful when I learned to set his fatigue high.  I've even thrown him out for an occasional start, which does knowck him out for a while.  It helps that I have a pretty good staff, because it is like going with an 11-man staff part of the time. 

http://www.whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx?pid=2774227

I have used this guy both as a set-up and a spot starter. (Durability 2)  He performed much better as a spot starter.  I never spent too much on him and would shuttle him to AAA between starts.  Always just liked having him around.  Be careful though, don't overpay, you just won't get many innings.  If you do shuttle, manage your minors, you don't want to waste any innings there, as I did this year.  http://www.whatifsports.com/HBD/Pages/Popups/PlayerProfile.aspx?pid=344522
this last year, I had to designate him every demotion, but found out that despite his whip of 1.07 and negligible payroll, nobody took him -- of course, he was always at about a 2(9) when going through.

I've used Hardball Dynasty – Fantasy Baseball Sim Games - Player Profile: Marino Martin as both setupA and closer with reasonable success until he totally melted down this past season (guys who only pitch 35 innings a season are prone to having "sample size blowups"). In the playoffs I turn him into a SP. 

If he has good enough ratings in other places and you have a playoff capable team, carry him on the roster and stash him in mopup or something.  Once you make the playoffs, give him one start per series and dominate.  If you don't have a playoff team and he is big league ready, shop him to a playoff team, they know his playoff value and will give you good return.