Collin Morikawa describes his process in choosing a new caddie after his second split from a caddie this season. (1:31)Morikawa discusses what he's looking for in a caddie after 2nd split this season (1:31)Open Extended ReactionsTwo-time major champion Collin Morikawa is in the market for a new caddie -- again -- after parting ways with Joe Greiner ahead of this week's Rocket Classic in Detroit. In a news conference Wednesday, Morikawa described Limbhasut as a "fill-in." Morikawa split with J.J. Jakovac, the only caddie he had had as a pro to that point, in late April. Morikawa said he wasn't sure who would be his caddie at next month's Open Championship at Royal Portrush Golf Club in Northern Ireland, the final major of the season.