Ryder, who made one in his first Twenty20 for his new province, was effective with the ball and claimed 1-21 from three overs. Last month, he scored a century against former side Wellington in the Plunket Shield in his first match following a six-month drug suspension.
• Meanwhile, Wellington will probably require a sporting declaration from Central Districts if their Plunket Shield clash at the Basin Reserve is to produce any sort of a result.
After resuming day three on 149-2 and firmly in control, Wellington were undone by Doug Bracewell and Tarun Nethula, who both grabbed four wickets to restrict the home side to 293.
Trailing by four runs heading into their second innings, Ben Smith (70) and Carl Cachopa (54) put on 97 for the second wicket, helping the Stags to 170-3 at stumps.
They will begin day four with a lead of 166 and, after the first round produced two draws, another stalemate is shaping as the most likely outcome.