To run out of steam means to lose momentum and fail, and in this context he could lose his stamina and fail if the match goes to five sets.
Context: It could be a long match tomorrow, and he could lose his stamina and fail if it goes to five sets.
Hypothesis: It could be a long match tomorrow, and he could run out of steam if it goes to five sets.

Is the hypothesis incorrect? (Yes, no, or unknown)?