Chelsea captain John Terry says he is undergoing platelet rich plasma therapy (PRP) in a bid to recover from his Achilles injury.
The 35-year-old, who is out of contract this summer, has missed Chelsea's last two matches, having only recently recovered from a hamstring problem which kept him out for six games.
Terry, who is expected to be out for another two to three weeks, posted a photo of himself in surgical scrubs on Instagram and used an emoticon of a syringe.
He wrote: "PRP Being injured is the most frustrating thing as a player. Working hard to get back fit."
The former England captain earlier on Monday posted a short video of himself in the gym, demonstrating his desire to return to full fitness.
Laboratory studies have shown that PRP can potentially speed up the healing process. PRP involves reintroducing a concentrated platelet solution derived from the patient's blood. Platelets, which along with red and white cells is part of blood, contain hundreds of proteins called growth factors.
PRP has been used by athletes in a range of sports, including golfer Tiger Woods. The practice is permitted by the World Anti-doping Agency, after it removed it from its prohibited list at the start of 2011.
WADA says on its website: "Despite the presence of some growth factors, platelet-derived preparations were removed from the [prohibited] list as current studies on PRP do not demonstrate any potential for performance enhancement beyond a potential therapeutic effect."
Terry made his 700th Chelsea appearance at Everton last month and his 701st in the draw with West Ham before the international break, but did not play in the 4-0 win at Aston Villa or the 1-0 loss at Swansea.
The defender in January said he would be leaving Chelsea this summer as he had not been offered a contract extension. The club insisted an offer could be forthcoming.
Last week, Antonio Conte was appointed Chelsea head coach for next season and is likely to have a major say on Terry's future.
Meanwhile, Terry has offered to pay the funeral costs of eight-year-old Chelsea fan Tommi Miller, who died following leukaemia on March 31.
Terry told the Cambridge News: "Having had the pleasure of meeting Tommi at a Chelsea game I was totally devastated to hear of him passing away.
"I'm sure his family and friends will give him the send-off he deserves."
Tommi's mum Ruth added: "I'm overwhelmed really, because Tommi was such a great fan of John Terry in particular. He was one of his favourite players."