Juan Martin del Potro urged Andy Murray to "keep fighting" after the Brit announced he would retire this year due to his troublesome hip.
An emotional Murray, 31, said on Friday the Australian Open could be his last tournament, although he would like to retire at Wimbledon.
But Del Potro, who has returned from multiple wrist surgeries to get back to world number five, wants the three-time grand slam champion to keep battling.
"Andy, just watched your conference. Please don't stop trying. Keep fighting," the Argentinian wrote on Twitter.
"I can imagine your pain and sadness. I hope you can overcome this. You deserve to retire on your own terms, whenever that happens.
"We love you @andy_murray and we want to see you happy and doing well."
Murray revealed he was struggling with hip pain when simply trying to put on his socks and shoes.
Among numerous tributes, Billie Jean King wrote Murray, whose fight for equality has been lauded, should look forward.
"You are a champion on and off the court. So sorry you cannot retire on your own terms, but remember to look to the future," she wrote on Twitter.
"Your greatest impact on the world may be yet to come. Your voice for equality will inspire future generations. Much love to you & your family."