The Marlins optioned Veneziano to Triple-A Jacksonville on Wednesday.
His demotion clears a spot on the 26-man active roster for lefty Ryan Weathers (forearm), who was reinstated from the 15-day injured list ahead of his scheduled start Wednesday versus the Cubs. Veneziano has a 4.86 ERA, 1.56 WHIP, four holds and a 15:8 K:BB across 16.2 innings with Miami this season, but he allowed four runs (including three home runs) over his last three outings.