McIlroy suffered ankle injury playing football in early June.
Johnson defeated Louis Oosthuizen and Marc Leishman in an enthralling playoff.
Jordan Spieth lies one shot off the lead to remain in contention for a third major.
Dustin Johnson leads after a delayed second day at St Andrews.
Johnson leads seven under par after the first day at St Andrews.
The 144th edition of the Open Championship begins on 16 July.
Fowler comes into his sixth Open off the back of a win at the Scottish Open.
Fourteen-time major winner has no plans to give up golf despite his recent decline.
Tournament favourite Jordan Spieth starts alongside Dustin Johnson and Hideki Matsuyama.
Jordan Spieth warms up for St Andrews test with victory in US competition.
Five-time major winner Phil Mickelson has supported Rory McIlroy's pullout from the upcoming St Andrews championship.
Rory McIlroy will not defend his British Open title at St Andrews.
BREAKING: McIlroy confirmed the news via a message to his Instagram followers.
McIlroy ruptured the ligament in his left ankle and suffered joint damage while playing football.
Spieth follows up his Masters success with victory at Chambers Bay.