The Professional Footballers' Association has backed calls from Jurgen Klopp and Pep Guardiola for the Premier League to re-introduce five substitutions, instead of the usual three.
The knock-on effect of the coronavirus pandemic has seen a more congested fixture list, with some managers insisting it is having an impact on players' wellbeing.
A change to the rules this season is possible, if a team puts forward a proposal. However it would need the support of at least 14 clubs and has already been rejected twice, so seems highly unlikely.
- Kevin De Bruyne misses pen in gripping City-Liverpool draw
- Trent Alexander-Arnold to withdraw from England squad with injury
- Man City 1-1 Liverpool highlights
- Get Sky Sports | Get a NOW TV Sky Sports pass
Manchester City are backing a change, but have only used an average of two substitutes per game this season. West Brom, Tottenham, Wolves, Arsenal and Newcastle have used all three.
After Trent Alexander-Arnold went off with a calf injury during Sunday's 1-1 draw at the Etihad, Liverpool manager Klopp said: "All the teams have to understand why it's so helpful. It's not an advantage, it's a necessity. 100 per cent.
"In all other countries it happens and here we make a bit more fun of the competition by having only three subs. That is really incredible, so we have to talk again."
Indeed, in all major leagues across Europe and in Major League Soccer in the United States, teams have voted to adopt the five substitute rule this season.
However, it would no doubt favour the bigger clubs. Whilst West Ham boss David Moyes has come around to the idea, other sides are standing firm.
One senior official at a top-flight club told Sky Sports News: "Our position hasn't changed. Purely and simply, the bigger the club, the bigger the advantage if you have five subs.
"Not all clubs have a huge squad with the depth of talent that some clubs enjoy and five substitutes will simply make life more difficult for smaller clubs."
The PFA has confirmed it remains in support of allowing clubs to use five substitutes.
"We told the Premier League we would support such a move on health and safety grounds for our members before the first vote and our position has not changed," a PFA statement read.
The rule has clearly divided opinion, but in terms of restoring integrity and honoring the two votes that have already taken place, it seems unlikely we will see any change before the end of the season.
Klopp: "In my understanding, it is a lack of leadership"
Klopp believes the Football Association should take action over the substitutes rule, or risk having more international players ruled out through injury.
"In my understanding, it is a lack of leadership," Klopp added. "It is the only big league where you have only three subs. Surprise.
"The FA has to be involved. Tonight we lost Trent Alexander-Arnold. I'm pretty sure Gareth Southgate is not fine [with that]. If we continue like this and hopefully we can play the Euros in the summer... if they happen, let's see who will be part of that."
Guardiola: "We don't protect players and that's why it's a disaster"
Guardiola says he fully agrees with Klopp that the limit must be increased: "All around the world it's five substitutions, but here we believe we are more special people," said Guardiola.
"We don't protect the players, and that's why it's a disaster. In this calendar, especially. I will demand, if the people allow, we have to come back to five substitutions. If not, it's difficult to sustain it."
Moyes: I've changed my mind over five subs
Moyes had previously been in favour of only using three substitutes but he admits he would now prefer the option of being able to have up to five replacements.
"I recommended to our board that we would vote for three subs and not more. I've got to say, my mind has changed now is because of player welfare," said Moyes, speaking after Saturday's 1-0 win over Fulham.
"I don't think I expected so many injuries. So many games in such a small period of time, whether it be that you're an international player or in the Champions League or the Europa League, has meant that the programme has been so congested.
"There have been no parties willing to give up any games, whether it be the Carabao Cup or any other cup competition. Nobody has been willing to give anything up.
"That's why now I would consider the change if it was there, that we could have more subs."
Pitch to Post Review: Pep's claim doesn't add up
Jasper Taylor is joined by Ben Ransom and Gerard Brand on the latest Pitch to Post Review podcast to discuss the weekend action in the Premier League as heavyweights Man City and Liverpool punch each other's lights out for 45 minutes, then cuddle on the canvas.
Did Liverpool's front four work, and could Gabriel Jesus replace Sergio Aguero? And in the Treatment Table, we reveal why Pep Guardiola's moan about the five subs rule simply doesn't add up.
Roy Keane believes Manchester City lack the firepower needed to win the Premier League this season, after their 1-1 draw with Liverpool.
Guardiola's side were a distant second to the Reds last season and eight games into the 2020/21 campaign they already trail Liverpool by five points, sitting 11th in the table, six off early leaders Leicester City.
Interestingly, Man City have scored 17 goals fewer than they had at the same stage of last season, and Keane believes with Sergio Aguero struggling with injuries, they aren't able to make their dominance count in matches - and criticised them for not investing in a striker in the summer.
"I know there were other positions they wanted to fill, a centre-half I suppose was a priority. They've got nobody but themselves to blame for being short on strikers. You have to have strength in depth - particularly if you're expected to challenge for all the major trophies. I don't see City winning the league this year."