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Phelps, Lochte, Franklin and Ledecky lead decorated field at Arena Pro Series in Mesa

Michael Phelps, Ryan Lochte, Missy Franklin, Katie Ledecky and 18 other Olympic medalists are expected to compete at this weekend's Arena Pro Swim Series in Mesa, Arizona. The meet, which serves as a tune-up for American swimmers before June's Olympic Trials, opens Thursday and continues through Saturday. Preliminary sessions are at noon ET, followed by 8 p.m. ET finals sessions.

Other U.S. Olympic gold medalists in the mix are Nathan Adrian, Tyler Clary, Allison Schmitt, Jessica Hardy, Conor Dwyer, Anthony Ervin and Dana Vollmer. Jordan Wilimovsky, who already qualified for the 2016 Rio Games in the open water 10k, is also slated to swim in Mesa.

But the meet is open for international swimmers, too. Notable international names include three-time Hungarian Olympian Katinka Hosszu, three-time Jamaican Olympian Alia Atkinson, two-time Olympic bronze medalist Arkady Vyatchanin and Danish bronze medalist Lotte Friis.

Reigning 2015 world champion Ledecky is set to face off against 2013 world champion Franklin and 2012 Olympic champion Schmitt in the 200m freestyle, surely a preview of the showdown set for Trials.

Ledecky is also slated to swim the 100m butterfly, 100m freestyle, 400m freestyle, 200m individual medley and her signature 800m freestyle, in which she is the 2012 Olympic champion, world record holder and seeded about 15 seconds ahead of the rest of the field.

Lochte, notoriously coy about what events he'll swim at Trials, is slated for the 200m freestyle, 100m butterfly, 200m butterfly, 100m backstroke, 200m IM and 100m freestyle this weekend in Mesa. He told media he felt like an "underdog" before the start of the meet.

Mesa is a notable meet for Phelps, who is set to swim the 200m freestyle, 200m butterfly and 200m IM. After 20 months of competitive retirement, Phelps debuted anew at the 2014 Mesa Pro Series. After being arrested for driving under the influence in September 2014, he sought treatment in Arizona. Following his six-month suspension from USA Swimming ended, Phelps again made his season debut at the 2015 Mesa Pro Series. Soon after the 2015 meet, he announced he would move to Arizona to continue to train with longtime coach Bob Bowman after Bowman accepted a head coaching position at Arizona State University.

NBC Sports Live Extra is streaming the April 15 and 16 finals sessions beginning at 9 p.m. ET, and the entire meet will be streamed on usaswimming.org. In addition, NBCSN will air next-day taped finals coverage on April 16 (6:30 p.m. ET) and April 17 (midnight ET).