The second serve is a confidence shot.
Grigor Dimitrov concedes his is still a work in progress.
Watch: Edmund Surprises Dimitrov
The third-ranked Bulgarian spit up seven double faults in a 6-4, 3-6, 6-3, 6-4, quarterfinal loss to Kyle Edmund.
Weeks after Dimitrov gave the fallen Brit a helping hand on court during their Brisbane quarterfinal, he continued a tournament-long trend of dishing double fault aid to opponents.
Dimitrov hit 13 aces and 15 double faults in a third-round win over 30th-seeded Andrey Rublev and won only 28 percent of second-serve points squeaking out a five-set win over Mackenzie McDonald in round two.
When his toss strays too far to the left, Dimitrov can land spinny second serves short in the box allowing opponents to attack.
The Nitto ATP Finals champion said he’ll review video to try strengthen his second serve.
“I really need to think about it,” Dimitrov said. “I've been thinking since day one, even Brisbane, I still felt that I have not served well enough. Yeah, obviously I'm going to watch quite a bit of video and see some of the stats.
“Definitely that's one of the things I've struggled a lot in the past week. That's one thing I know if I can turn around, make sure I'm a bit more consistent. Even now, I felt like some of the matches I was serving pretty much all the matches over 50 percent It's just the winning percentage on the second serve was pretty low, made quite a bit of double-faults. Can only blame myself on that.”
Photo credit: Mark Peterson/Corleve