The San Francisco 49ers' defeat to the Cleveland Browns was defined in part by some ugly scenes before the game had even kicked off.

Neither team was punished for their pregame fight, but the NFL made it clear it does not want a repeat.

ESPN reported on Sunday that it had obtained a memo in which the league told all 32 teams fighting is "irreconcilable" with the league's values and is "never acceptable". 

The memo set out potential discipline that could be handed down for future fights, with players or club personnel involved in such incidents before or during a game subject to ejection, suspension and/or a "significant fine".

Teams whose players or personnel fight could face the prospect of forfeiting a draft pick and/or being fined. On top of that, the league added that teams who have players or personnel enter an existing fight may be "subject to more significant accountability measures".

"Fighting is never acceptable, as it risks unnecessary injury to players, coaches, officials, and other game day personnel," the league memo read. "These actions send an inappropriate and unacceptable message to players, coaches, and fans at all other levels of the game."

San Francisco's fight with Cleveland came a day before the Dallas Cowboys and Los Angeles Chargers were also involved in a fracas prior to their Monday Night Football clash.

Though none of the players from any of the four teams were subject to discipline this time around, the NFL warned it intends to "strongly enforce" its policies going forward.

The 49ers will play some highly charged games down the stretch of what they hope will be a special season, but it could prove costly if they let their emotions boil over again at any point in the campaign.

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