Why would you mess with Sanchez, he's picked up where he left off last season and has been excellent.
If it ain't broke, don't fix it!
Between AAA and PHL, he started 26 games and threw 149 IP last season. He's your 4th starter, period.
His 2-seamer velocity is up this season, 92.3 to 94.2. It's not as effective, as he's getting used to throwing harder, I suspect he'll dial back a little and improve command, but his changeup is plus plus and the slider is a plus pitch.
Neither Turnbull or Walker are suited to the bullpen.
Walker last three seasons, 29, 29, 31 starts, 159, 157, 172 IP
I think they'd have to be used in a long relief role throwing multiple innings to have value in the pen.
Walker lives and dies on the splitter but his other pitches are meh.