Barcelona coach Tito Vilanova underwent throat surgery on Thursday to treat the reappearance of a tumour on a saliva gland.
The Spanish club said his progress will mark his hospital stay, and his doctors were maintaining their plans of treating Vilanova with chemotherapy and radiotherapy for up to six weeks.
Barcelona captain Carles Puyol said "the operation went well.''
Barcelona made the announcement that Vilanova had fallen ill again on Wednesday.
The club said Vilanova might be able to return to the sidelines while continuing his treatment. It did not provide a timetable for his return.
In the meantime, Vilanova's assistant coach, Jordi Roura, has taken over training and will coach the team for Saturday's Spanish league game at Valladolid. Roura has been on Barcelona's coaching staff since 2009.
"Yesterday was a hard day, but (Vilanova) came to the dressing room and explained everything to us and boosted our spirits,'' Puyol said.
"He hadn't even left yet and he was saying he couldn't wait to be back. Today we feel better because the news is good.
"We have to keep playing the same way, train as hard as we can, (and)look forward to (Vilanova's) return.''
Puyol said the club's decision to let Roura take over for now was the correct one.
"He has been working with us for years. He knows the team perfectly,'' Puyol said.
"Our way of doing things won't change. We are in good hands.''
The 44-year-old Vilanova had surgery to remove a tumour from a saliva gland in November 2011 when he was Pep Guardiola's assistant at the club.
Vilanova had chemotherapy and radiotherapy at that time and returned to the squad in 15 days, ahead of schedule.
He took over for Guardiola at the end of last season after five seasons as his assistant, four with the first team and one with the B team.
Under Vilanova's guidance, Barcelona have made their best ever start to a season, winning a Spanish record 15 of their first 16 league games. The club lead the standings with 46 points, nine ahead of Atletico Madrid and 13 in front of defending champions Real Madrid.
Barcelona are also the favourites for this season's Champions League. On Thursday, Barcelona drew AC Milan in the first knockout round. The opening leg of their two-game tie will be played in Italy on February 20.
The announcement of Vilanova's ailment on Wednesday coincided with the return of defender Eric Abidal to his first team practice since undergoing a liver transplant eight months before.
Previously, Abidal had to have a liver tumour removed in March 2011, but he made a speedy recovery before it was discovered that he needed the transplant.
Puyol said Abidal's second return was a boost, especially with the health of their coach again in doubt.
"These are always tough blows. You are never prepared,'' Puyol said.
"The example of Abi, who can already play again, gives strength to the entire group.''