The 22-year old travelled back to his homeland of Uruguay last weekend, after the 1-0 loss at Liverpool, after a family member passed away.
Saints boss Nigel Adkins granted Ramirez compassionate leave and thought he would still be away for Saturday's vital home clash with the Royals but he is thrilled to have the attacking midfielder back.
"Gaston went back to Uruguay last Sunday for compassionate reasons," said Adkins.
"He is back on the training ground tomorrow morning so we will have a good chat with him then.
"He has done a bit of training over in Uruguay so that is beneficial and I am sure he will be desperately wanting to play at the weekend.
"We'll have a good chat with him in the morning about how he is feeling but, knowing Gaston, he'll want to play."