Robbie Manson will take the single sculls seat at the championships, Rowing New Zealand (RNZ) said on Thursday.
The move for the 39-year-old Drysdale had been signalled last month when Manson beat him in the singles sculls at the World Cup meeting in Lucerne.
RNZ had set that meeting as the final selection race between the pair after a series of duels at training and in competition all season, but there was no guarantee that either would be picked to row in another crew in Bulgaria.
Drysdale, who won his second successive Olympics gold in the single scull at the Rio Games in 2016, took a year off from rowing last year with an eye on returning and going through to the Tokyo Games in 2020.
Manson replaced the five-times world champion in the single scull last year and broke the world record but was injured ahead of the world championships in Florida, where he finished fifth.
The pair had been set on the collision course when Drysdale returned to RNZ's high performance programme late last year.
Drysdale finished fourth in the World Cup meeting in Switzerland and said at the time he would be happy to be considered for any other crew for the championships in Plovdiv from Sept. 9-16.
"If I can strengthen another boat, I'm available," Drysdale told the New Zealand Herald last month.
"As soon as the worlds are over, I'll be back in the single aiming for next year's selection but I know not every boat will be open for selection.
"Both Robbie and I were aware that whoever missed out would take what we're given."
(Reporting by Greg Stutchbury; Editing by Sudipto Ganguly)
