Manchester City manager Pep Guardiola said on Friday that his Premier League champions had been hit by fresh coronavirus cases ahead of their match with Chelsea.
The league leaders were without 21 personnel, including Guardiola and seven senior players, for last week's FA Cup third-round win at Swindon after positive tests for Covid-19.
Some first-team regulars have returned ahead of the home match against second-placed Chelsea on Saturday, which is still expected to go ahead as scheduled.
Guardiola, speaking at a pre-match press conference, said: "Some people are coming, some people are positive again. When you have tested once, twice negative you come back. Otherwise not.
"We have some new cases but they want privacy, so I cannot tell you."
The festive schedule in English football's top-flight was severely disrupted by postponements, with clubs struggling to field sides due to rising Covid cases and injuries.
City are 10 points clear of Chelsea at the top of the table, with both clubs having played 21 of their 38 league games this season.
Tuchel famously got the better of Guardiola in last season's Champions League final and the City boss said he had become a better manager after watching his rival at work.
"He is so creative, one of the few managers I learn from to become a better manager myself," said Guardiola. "He is excellent in all departments.
"Since he was at Mainz, Borussia Dortmund and here, I have always enjoyed watching his teams, the way he is playing and his approach.
"I think he dignifies and makes world football better. When you find a manager that is always positive in the way they play it is good."