Santos (biceps) has begun throwing at the Mariners' extended spring training in Arizona but remains without a timetable for return, MLB.com reports.
Mariners general manager Justin Hollander noted Monday that the team's medical staff doesn't believe there's a kinetic chain issue with Santos after he also missed over three months earlier this season with a right latissimus dorsi strain. However, whether Santos can return before the end of the season remains an open question, and given his checkered medical history the last few months, the team may opt to play it safe.