Michel Gonzalez became the second coach to lose job in La Liga on Monday when he was sacked by bottom side Getafe.
Barcelona president Joan Laporta had said a few hours before kick-off that Koeman would continue as coach 'regardless of the result' at the Wanda Metropolitano.
Benzema and Vinícius Júnior had been carrying Madrid's attack so far, with at least one of them scoring in five of the first seven matches.
Little by little Eduardo Camavinga is making his case to become a regular starter in Carlo Ancelotti's team, which on Saturday hosts Villarreal to defend its La Liga lead.
Frenkie de Jong was sent off in the 65th minute at the Ramon de Carranza stadium but holding on for a draw will earn little credit for Koeman, who was also shown a red card in injury-time.
Benzema scored twice to reach 200 league goals but Madrid also got a hat trick from Marco Asensio on its way to a comfortable 6-1 win over Mallorca.
Ronald Araujo, another central defender, was also thrown into the attack as Barca sent in 54 crosses in search of an equaliser.
La Liga's reigning champions have now drawn two and won three of their opening five games.
The veteran striker went on as a 71st-minute substitute with Rayo 1-0 ahead.
Barcelona have made a solid start in La Liga and for now, the hope is an upturn will postpone bigger, and more expensive, decisions until later.
Barca said both players are "unavailable for selection" and their "return will depend on the recovery".
Griezmann was replaced in the 58th by João Felix, who hadn't played this season because of an injury.
La Liga president Javier Tebas delivered some familiar broadsides on Sept 7 about PSG benefiting from state funding, followed by fresh digs against the club for signing Lionel Messi from Barcelona.
Fernando Morientes, who has worn the jersey of Barcelona's eternal rivals Real Madrid, is in admiration of the gesture made by players like Gerard Piqué, Sergio Busquets and Jordi Alba
The Colombian's last club was Turkey’s Galatasaray where he played from 2019 until the end of last season.