Mitch, I think you are missing the point. Depending on who we have to replace Porcello, you would still have slugs filling in.
Now, ifwd Sanchez and kept Porcello, the lesser the chance of any slugs starting for DET.
Keep in mind that Porcello has been about 2 Wins Above Replacement level over the last 3-4 years. The Tigers have not received replacement level production from any of the above "slug" starters.
Also, while Porcello only averages 5.92 IP/GS, the "slugs" have averaged 4.34 IP/GS.
2010-2012
Verlander 7.14 IP/GS
Fister 6.46 IP/GS
Scherzer 6.02 IP/GS
Porcello 5.92 IP/GS
2012 AL AVG Starter 5.88 IP/GS
But I think you're not thinking "maybe the Tigers could get a need for him?" And I don't think its Porcello or slugs. Get a starter, trade Porcello.