Nelson led the NL in walks in 2016 .
If his control problems continue , it 's not hard to imagine he could wind up back at Triple - A at some point next season , since he 's optionable .
Nelson led the NL in walks in 2016 , and if his control problems continue , it 's not hard to imagine he could wind up back at Triple - A at some point next season , since he 's optionable .