"Such a headache!" the insider said of the last-minute scrambling. According to another source, however, the strategic separation of the two wasn't just limited to the Staples Center auditorium on Sunday, Feb. 10.
Staff members also had to keep the pair "from crossing paths" on the red carpet and throughout the ceremony. But the root of the country contention isn't coming from Swift, a friend of the singer insists.
"Taylor feels Carrie is always rude to her, so she steers clear of her," the pal told Us. (A Grammy rep countered: "No requests were received from either artist.")
A source close to Underwood, 29, similarly denies any feud, saying instead that the singer is just "shy."
The American Idol alum gave a rousing performance of her hit "Blown Away" during Sunday's awards ceremony, but Swift didn't seem too impressed.
"After Carrie performed, Taylor didn't stand," an eyewitness told Us. "Everyone else did."
An energetic Swift was seen dancing and singing along to other performances throughout the night with her pal Claire Waterman, daughter of celeb jewelry designer Cathy Waterman.
To be fair, however, Swift, 23, may not have been paying too much mind to Underwood at the Grammys -- she had other musicians to avoid as well. The singer, who opened the show with an explosive rendition of her hit "We Are Never Ever Getting Back Together" that took a dig at ex Harry Styles, also made sure to steer clear of John Mayer and his current girlfriend, a mint green-clad Katy Perry, 28.
Perry and Swift have previously been photographed smiling and happily posing together at events.
Mayer, 35, and the "Dear John" singer briefly dated in 2010.
This article originally appeared on Usmagazine.com: Taylor Swift Disses Carrie Underwood, Avoids Ex John Mayer at Grammys 2013