And once it got to the fifth set, we knew what would happen there because, after all, del Potro has only defeated Federer twice in 13 career matches.
Federer was cool as cucumber winning the third set 6-2 and fourth set 6-0 before turning his attention to the fifth. It took him less than an hour to take the third and fourth sets from del Potro and the Argentine was visibly crushed down the stretch.
He rallied in the fifth set to win three games, but Federer was simply too good when it mattered most. In the end, the world's No. 3 player advanced with a 3-6, 6-7 (4), 6-2, 6-0, 6-3 victory.
A year ago, Federer eliminated Djokovic in the semifinals before losing to long-time rival Rafael Nadal in the final.
Rafa has won the French Open six of the last seven years and has looked absolutely dominant so far this year. He's made it well known that Roland Garros is his court and everyone else is just playing on it, even Federer.
The Swiss star made his showdown with del Potro more difficult than it had to be, but nobody is more calm under pressure than the 16-time Grand Slam winner.
Should he get back to the final against Nadal, he'll need all that composure and more.