Half of the weekend's Premier League fixtures are now off after four more games were postponed because of Covid-19 outbreaks.
The latest games affected are Southampton v Brentford, Watford v Crystal Palace, West Ham v Norwich and Everton v Leicester.
Earlier on Thursday, Manchester United's match with Brighton on Saturday was called off, along with Leicester City's game with Tottenham on Thursday, which is part of the league's midweek programme.
On Wednesday Brentford boss Thomas Frank called for this weekend's top-flight fixtures to be postponed to let clubs deal with the outbreaks but the Premier League is so far resisting that.
"All other fixtures due to be played this weekend are currently scheduled to proceed as planned," it said in a statement.
Liverpool players Fabinho, Curtis Jones and Virgil van Dijk will also miss Thursday's match with Newcastle after suspected positive tests, although manager Jurgen Klopp said that the club did not ask for a postponement.
"Honestly, I think at one point we have to make clear what exactly the rules are, but of course with three players out and this squad we wouldn't have asked to not play a football game," he told BT Sport.
Thursday's other match between Chelsea and Everton is set to go ahead despite four of the London side's players testing positive - Romelu Lukaku, Timo Werner, Callum Hudson-Odoi and the injured Ben Chilwell.
A total of nine top-flight matches have been cancelled over the past week, the others being Tottenham's match against Brighton last Sunday, Brentford's game with Manchester United on Tuesday and Burnley's match against Watford on Wednesday.
The Premier League said there was "an increase in positive Covid
-19 cases" at Leicester on Thursday, while Manchester United have an ongoing outbreak.
United said they would also suspend training at their Carrington base for "a short period to help reduce risk of further transmission".
The club added in a statement: "The health of players and staff is our priority. Given the number of players and support staff having to isolate due to Covid
-19, the club had no option other than to request the match be rearranged.
"We regret any disappointment and inconvenience caused to fans by the postponement."
Leicester manager Brendan Rodgers said on Wednesday that an initial request to cancel their game with Tottenham had been rejected, with the club expecting to be without nine players because of Covid
-related issues and injuries.
Spurs also wanted the game postponed to use the date to play their Europa Conference League game with Rennes, which was called off last week after a Covid
"In light of the new information, Leicester applied [on Thursday] for the fixture to be called off due to an ongoing outbreak within the squad, which has resulted in more players and staff testing positive for Covid
-19 today," read a Premier League statement.
"This has left the club with an insufficient number of players available to fulfil the game."
A Leicester statement read: "Given the increase in positive tests among first-team personnel, first-team operations at Seagrave [training ground] will now be closed for 48 hours, serving as a circuit breaker to help reduce the risk of further infection.
"First-team players and staff will undergo a subsequent round of testing on Saturday."
The Premier League added: "Regarding Manchester United's game on Saturday [against Brighton], the club continues to have an ongoing Covid
-19 outbreak within their squad, which has left them unable to field a team for the match at Old Trafford.
"A significant number of Covid
-19 cases led to their game against Brentford being called off earlier this week, and today [Thursday] additional positive tests have been confirmed."
Brighton boss Graham Potter questioned how long "football can continue on the path it's on" after revealing his Covid
-hit team wanted Wednesday's game against Wolves, which they lost 1-0, to be postponed.
The Premier League said it "assesses applications on a case-by-case basis" and decisions are "based on existing rules and Covid
-19 postponement guidance issued to all clubs".
It added: "[The board] will assess a number of factors, including the ability of a club to field a team; the status, severity and potential impact of the Covid
-19 outbreak at the club; and the ability of the players to safely prepare for and play the match.
"The board must also consider the wider risks to the opposition and other people the club may come into contact with."