After the draw for Miami was made, the prospect of a match between Federer and Wawrinka for the second time in as many tournaments was a distinct possibility.
Last week, Federer beat Wawrinka 6-3 6-4, his sixth consecutive win over his fellow Swiss.
For them to face off again in Miami, Federer had to beat Radu Albot and Wawrinka to defeat Krajinovic.
And Federer admitted it was “not ideal” to have his friend Wawrinka potentially in his path to the final again.
“I prefer not to have him in my draw. I prefer to never have him in my section, but it is what it is,” he said.
“As a player, I think you always look at your first couple of rounds, so I know that there’s a chance there and a possibility, so we’ll see what’s going to happen.
“But it’s definitely not ideal that we’re maybe going to play each other in back-to-back tournaments.”
But after winning the first set against Krajinovic, Wawrinka’s level dropped as he struggled with injury.
And Krajinovic fought back from trailing 2-4 in the third set tiebreak to win the match 5-7, 6-2, 7-6.
Speaking after the match, Wawrinka admitted mistakes cost him the match.
“I would not say I had it in my hand,” he said.
“I knew it was going to be a complicated match.
“I had chances at 5-2 in the third set tie-break.
“Unfortunately, I made mistakes, I played a little too fast.
“I fought with everything I had today, it’s a shame to lose.”