Aaron Sanchez since 2017 is 8-18 and has thrown 219.2 innings, given up 234 hits, 123 walks with 175 strikeouts. His ERA is 5.00, his FIP is 5.17 and his xFIP is 5.15. Not only should Sanchez not be extended you could make an argument that he should be DFAd. At the very least he should not be starting another game.