State Wellington Firebirds bowler claimed five State Auckland Aces wickets in the first day at Christchurch’s QEII Park.
Having chosen to bat first, the Aces posted 242, with - fresh from a career-best 160 last week - top-scoring with 85 having forged a partnership of 48 with captain (62).
O’Brien responded to Firebirds coach Anthony Stuart’s call for an improved performance, and led the attack well with five wickets for 57 off 23 overs.
BLACKCAPS tourists (two for 52) and (three for 43) also claimed wickets as Auckland’s innings was halted within 94 overs.
The Wellington reply stood at two without loss after five overs at stumps.