The German took heat from her opponent and the crowd on Monday at the Open.
Grand Slam champions bumped into each other on the street and will reunite in round two of the US Open.
Relegated to Court No. 5, fourth-seeded Holger Rune failed to survive the US Open first round.
No. 8 seeded Maria Sakkari considers a break after suffering her third straight Grand Slam opening-round exit.
"The mental side was not that easy as restore the arm was," Dominic Thiem said.
The former champion has been dealing with a stress fracture in her back.
The 2014 US Open finalist has been snake-bitten by injuries.
