West Ham striker Diafra Sakho is unlikely to play again this season because of the back injury he suffered in November.
He has only played twice all season, having also missed the start of the season with a back problem.
The 27-year-old has now returned to light training following surgery.
"Diaf is essentially at the start of his own personal pre-season training schedule," Hammers medical boss Stijn Vandenbroucke said.
"When players return from their off-season, they will go through four to five weeks of pre-season work to build up their strength and fitness.