Mickelson had completed his day at Torrey Pines earlier in the day, Mickelson watched as Rahm pulled off two superb birdies on the 17th and 18th holes to take the lead from Louis Oosthuizen. After his birdie on the 18th, Mickelson took to Twitter to share in Rahm's excitement.
"Jon Rahm’s putts on 17&18," Mickelson remarked. "AMAZING!!"
After sinking those birdies, Rahm had to wait a while longer for Oosthuizen to reach the 18th hole before he could be declared the winner. But when he was, Mickelson, his family and friends were all waiting to congratulate him.
Between the 2018 Masters and last month's PGA Championship, Rahm has finished in the top 10 seven times. This year alone he's finished in a tie for fifth at the Masters and a tie for eighth at the PGA Championship.
Close losses were starting to become a signature for Rahm. Mickelson and Tiger Woods are the only two active golfers with more second-place finishes at PGA Tour events than him.
His forced withdrawal from the Memorial Tournament several weeks back only added to the sense that it might take ages for him to finally get over the hump.
However, thanks to that win at the U.S. Open, there's no longer any denying that he's one of the elite golfers.
And Phil Mickelson couldn't be happier to see it.