The good news is that Zverev is showing the kind of resilience required to win seven matches in two weeks, a trait he is proud of.
“Look, it would be nice not to have to do it every single time, but if I have to do it, it's nice to know that I can,” he said.
“Obviously I don't do it on purpose. I don't go into the match and say, 'OK, my tactic is I'm going to be a break down, I'm going to fight back and come back'. That's not how it works. I'm a break down most of the time because I played unfocused games or the opponent played well.
“Today, especially last two sets, they could have gone both ways, especially the third. The second I thought I was in control more.”
Safiullin, ranked 182, won the junior title at the Australian Open the year after Zverev took it, but injuries have prevented the Russian from breaking through at the top level of the Tour.
On Wednesday, though, he showed plenty of fight and talent, leading by a break in the second and third sets before Zverev fought back to clinch victory.