AC Milan's players are fully behind under pressure head coach Gennaro Gattuso, according to Ricardo Rodriguez.
That defeat left Milan second in Group F behind Betis, and just two points above Olympiakos in third.
Gattuso claimed afterwards that it would be fair for his position to be under review, despite Milan having gone unbeaten in eight games in all competitions prior to their derby defeat.
But Rodriguez has insisted that Gattuso, who took charge in November 2017, has the squad's full backing.
"We lost two games and we are angry," the former Wolfsburg defender told Sky Sports.
"But to get out of this period we have to remain calm and focused.
"We're fine with Gattuso, now we play Sampdoria, we have to prove to be strong."
Milan sit 12th in Serie A, six points adrift of the Champions League qualification places, having won three of their eight league games this term.
They will have a chance to get back on the winning side of things on Sunday when they host Sampdoria at San Siro, before hosting a midweek clash match with Genoa.