BARCELONA (AP) ― Rafael Nadal’s doctor says the 14-time Grand Slam winner will receive stem-cell treatment on his ailing back.

Angel Ruiz-Cotorro told the Associated Press by phone on Monday that, “we are going to put cells in a joint in his spine” next week in Barcelona.

The Spanish tennis star was already sidelined for the rest of the season after having his appendix removed last week.

Ruiz-Cotorro, who has worked as a doctor for Nadal for the past 14 years, said Nadal’s back pain is “typical of tennis” players and that the treatment is meant to help repair his cartilage and is similar to stem-cell treatment Nadal received on his knee last year.

He said Nadal is expected to return to training in early December.

Several NFL players and baseball players have received stem-cell treatment. Nadal’s fellow Spaniard Pau Gasol, center of the Chicago Bulls, received stem-cell treatment on his knee in 2013.

Nadal experienced severe back pain during the final of the Australian Open in January when he lost to Stan Wawrinka.

“(Nadal) has a problem typical in tennis with a back joint, he had it at the Australian Open, and we have decided to treat it with stem cells,” Ruiz-Cotorro said.

He said that stem cells were recently extracted from Nadal for a cultivation process to “produce the necessary quantities.”