Michael Phelps once opened up on his approach towards the rivalry with his fellow teammates. Although Phelps enjoyed an unparalleled swimming career, he faced fierce competition from multiple contemporaries, including Ryan Lochte, Ian Crocker, Aaron Peirsol, Peter Vanderkaay, and Conor Dwyer.
Phelps once reflected on the intense rivalry he had with Crocker. They both competed against each other in the 100m butterfly event at the 2004 Athens Games and the World Championships in 2001, 2003, 2005, and 2007. Phelps even referred to his 100m butterfly event defeat against Crocker as 'one of the biggest beatdowns he ever took.'
In an interview in 2009, Phelps reflected on the fiery rivalry he enjoyed against Crocker while remembering the text he received from him after nearing his 50.40-second 100m butterfly world record registered at the 2005 World Championships. Phelps recorded 50.48 seconds in a competition when he received a composed text from Crocker.
"Crock actually texted me after and wished me all the luck and telling me that was my record," Phelps said. "That meant a lot, from a competitor and a friend and a classy guy. We had amazing battles back and forth. Those are something I definitely miss." (via www.espn.in)
Michael Phelps once opened up on the toughest defeat he suffered against Ian Crocker

Michael Phelps once opened up on the toughest defeat he suffered against Ian Crocker in the 100m butterfly. Phelps reflected on the faceoff in the event at the 2005 World Championships in Montreal. Crocker defeated Phelps by an entire body length in the last 40m of the race. While Crocker dominated the race with a world record of 50.40 seconds, Phelps settled in second place with 51.65 seconds.
"Ian Crocker gave me one of the biggest beatdowns that I probably ever took in 05 ad on," Phelps said. "Back-to-back days in 2003-2004, I came back and won the gold medal in the 200 fly and the 100 fly by 4100 of a second in 2005 World Championships, he literally beat me by a body length in 40 meters. In the last 40 meters of the race, and I was second, and that was probably to this date, the biggest beat down I've ever taken in my life, and that frustrated me to no other." (via sportlane.com in 2021)
Michael Phelps reclaimed his victory in the event over Crocker at the 2007 World Championships.