Newcastle were booed by supporters during the 3-0 loss to Watford at St James's Park on Saturday, a fourth successive league defeat that dropped them to 14th place, four points above the relegation zone.
Another setback might raise questions about their ability to survive in the top flight as owner Mike Ashley continues to negotiate the club's sale to PCP Capital Partners, which has had one reported bid of 260 million pounds rejected.
Benitez did not comment on the uncertainty around the club's ownership but the Spaniard said the fans must back the team to ensure results improve.
"A message for our fans - stick together. You see what we have and the players are giving everything. They can manage if we stay calm," he told a news conference on Monday.
"We have to support our team; to support our players. If they make the worst mistake in football history, we stick together."
Striker Joselu has come in for particular criticism, with supporters openly calling for the introduction of Aleksandar Mitrovic during the game against Watford.
But Benitez was quick to defend the 27-year-old, who was replaced by the Serb after 69 minutes.
"I think he is doing a lot of things right. He is doing a great job for the team & he is making the rest of our team feel more comfortable".
Benitez signed the 27-year-old for five million pounds from Stoke City, a signing that reflected Ashley's reluctance to invest too deeply in the squad ahead of the club's sale.
"If you want to sign a striker who'll score 20 goals, you must pay 40 million pounds," he said. "If you sign an average striker, it's 15 million pounds, or 10 million pounds if they can kick it forward. We didn't do it. That's the situation we're in."
Benitez did not confirm who will start up front against Albion.
"The fans appreciate that this group of players really care about the shirt. We have a difficult month. We have 14 points. It's a good position but we are not happy - it could be better, it could be worse."
(Reporting by Neil Robinson, editing by Ed Osmond)
