Returning to Arthur Ashe stadium for the first time in two years after she missed last year's tournament with injury, a ruthless Sharapova made it crystal clear she was not going to let friendship stand in her way of a second title at Flushing Meadows.
She made an unsteady start to the year's final grand slam falling behind 2-4 in the opening set, before she switched into top gear storming through the next 10 games.
"We spent a lot of time in the juniors away from the courts practicing a lot together, competing against each other," Sharapova said of her long-standing relationship with Kirilenko. "We certainly have a big history together.
"But when you go out on the court, it's always that fine line between; of course you want to be the winner, you have to face that person as a competitor, not someone that you've known for years and developed a friendship with.
"It's always a tricky balance, I guess."
The similarities between the two Russian right handers is striking.
Both are tall, though Sharapova still stands about six inches (15 cms) taller than Kirilenko, they are both 27 and made their professional debuts within months of each other in 2001.
Their careers, however, have taken vastly disparate paths.
Kirilenko has won six career titles while Sharapova has won half that many already this season including the French Open.
With 32 titles Sharapova, a former-world number one and five-time grand slam winner has banked over $30 million in prize money, Kirilenko $6.7 million.
After missing last year's U.S. Open, Sharapova reveled in her return, soaking up the atmosphere on the massive Arthur Ashe center court.
"It's just full of energy," the fifth seeded Russian said. "They're loud and passionate. You just feel the sports lovers are there.
"I think you feel the goosebumps when you go out on a night match on Arthur Ashe."
While Sharapova's slow start offered the briefest moment of suspense, the form book offered not a hint of a possible upset.
In 44 previous grand slam appearances Sharapova had lost in the first round only three times, two of those coming in her rookie season.
She has won 41 of her last 42 first round matches at slams; her solitary loss in that time coming at the 2010 Australian Open to Kirilenko.
But there would be no upset on Monday for Kirilenko, who has been hampered by knee and wrist injuries this year and won two matches in six tournaments.
"I thought there was a few times where I could have broken her in the beginning of the match," said Sharapova, who will next meet Romania's Alexandra Dulgheru.
"But I think she started off playing well and solid.
"Despite not taking those opportunities in a couple of her service games, I felt pretty good, especially towards the end of the match."
(Reporting by Steve Keating in Toronto. Editing by Greg Stutchbury)