Record number of men's players retire in Round 1 of US Open

Midway through Day 2, the men's draw at the 2015 US Open has lost more players to retirement in the first round than any other in the Open era.

With Ernests Gulbis, Thanasi Kokkinakis, Aleksandr Nedovyesov, and Marcos Baghdatis all pulling out of their matches Tuesday, the first-round total is up to a record 10 retirements, with cramps and dehydration the chief culprits. The previous high at the US Open was seven.

World No. 16 Gael Monfils headlines as the top-ranked on the list of retirees after withdrawing in the third set Monday night.

The total also doesn't include those who saw their matches through despite vicious cramping - like Vasek Pospisil, who instead of retiring simply dropped his final two sets 6-0, 6-1.

With the hot and humid conditions that have seen midday temperatures hit the mid-90s reportedly expected to continue through the second round, that number will likely keep rising.

One in particular to keep an eye on: world No. 10 Milos Raonic, who canceled his practice session Tuesday due to back spasms.