Robson, who reached a career-high ranking of No. 27 in 2013, has been unable to play since having right wrist surgery last June. The Brit is hitting again where she trains in Florida but she is not yet ready to compete, TENNIS.com has learned.
On the American side, world No. 53 McHale hopes to play Monterrey after suffering a shoulder injury. She has not played since the Australian Open this season, losing in the second round.
Hampton, 25, missed almost the entire 2014 season due to hip surgery. She recently said that she is hitting again, but has yet to decide when she will return. Hampton reached a career-high No. 24 ranking in 2013, after reaching the fourth round of Roland Garros that summer.