Sir Alex Ferguson has certified that Europe's top club coaches are split over the wisdom of using sin bins to punish footballers during matches.

Ferguson said the issue was squarely in the spotlight at a closed-door meeting of 18 coaches, which he chaired at the Swiss base of European football's governing body UEFA.

"That was quite a long discussion, on the various aspects of a different nature: serious foul, simulation, disrespect to the referee," Ferguson told reporters.

"But we couldn't get to an agreement about it because it's such a controversial decision to change from what we know to a sin-bin," said the former Manchester United coach, who retired in 2013 after 26 years in charge.

"I think that simulation by players has become a disease in the game. There's no question about that," he added.

Temporarily excluding an offending player from a match is a disciplinary tool in rugby union and league, or ice hockey.

Proponents say that what is good enough for those sports is also worth considering in the world of football.

Critics underline that football referees already have four degrees of sanctions for foul play- a free-kick, a penalty, a booking or a dismissal, and argue that a fifth option is pointless.

Ferguson noted that referees were also divided over the issue.

The two-day UEFA meeting, which is an annual event, drew names including Arsenal boss Arsene Wenger, Chelsea's Jose Mourinho, Real Madrid's Carlo Ancelotti, Luis Enrique of Barcelona and Bayern Munich coach Pep Guardiola.

"The area we spoke most about was tactical fouls, which prevent a player from progressing in the match, someone's on the halfway line and he pulls the jersey back, that was discussed," said Ferguson, adding that that was a clear yellow card offence.

Ferguson also said he believes that the group stage of the Champions League is ever more evenly-matched in competitive terms.

"The third team in the group is getting closer to the second and first," he said.

"Anyone going into the Champions League today has an opportunity," he added.

Ferguson said the coaches also assessed the continued relevance of the away goals rule, which can see clubs stumble or advance in  European competition if the aggregate score is a draw.

"From a personal point of view, when I was playing at home, I used to say to myself, don't lose a goal, because in the away game, you know you have to score," Ferguson said.

But tactical developments have shifted the debate, he explained, noting that strongly-manned counter-attacks rather than a calculated, defensive approach were now the watchword.

"If we go back say 30 years, counter-attacking was maybe one, maybe two players. Today counter attacks have players flooding forward in fives or sixes, really positive, quick passing," he said.

There was also debate about when the international transfer window should close, given that it does not coincide with the calendars of various European leagues.