Dwight Gayle is set to miss this afternoon’s game against Preston North End with a hamstring problem.
And Mitrovic – who scored two goals in Wednesday night’s 6-0 win over Simon Grayson’s side in the EFL Cup – is on standby to make only his second league start of the season at Deepdale.
United manager Benitez – whose side leads the Championship by three points – has repeatedly told the striker, second-choice behind 11-goal leading scorer Gayle, to be patient this season.
“Our message was very clear,” said Benitez, who will be without midfielder Jack Colback for the Preston game.
“We will have suspensions and injuries. You see Colback now from the challenge the other day.
“You need a good squad and everybody has to be working. That’s the reason why we were sending the same message. We knew this could happen.”
Mitrovic – whose only previous league start came in Newcastle’s 6-0 win over Queens Park Rangers last month – was booked for taking his shirt of to celebrate his second goal in the cup game against Preston.
And the 22-year-old, looking to score a hat-trick, also tried to take the ball off designated penalty taker Matt Ritchie late in the game.
Asked about the yellow card he got for taking off his jersey, Bentiez said: “It’s a silly thing to do as you don’t need to do it.”
Benitez also felt challenging Ritchie over the penalty made “no sense”.
Benitez said: “This one has been a conversation with the whole team, because these are things that are important for the rest of the team too.
“To be booked for this makes no sense. They need to know that arguing to take a penalty when we have already decided on a penalty taker makes no sense.”
Benitez has been helping Mitrovic – who was sent off twice last season – “manage his temper”.
“Mitro, in terms of working, is working very hard,” said Benitez. “In terms of his mentality, he’s a young player. He’s very emotional. It’s a question of time.
“When I came last year I had two or three conversations with him, trying to manage him a little bit.
“He’s getting better. The other day he was so excited. You can see it’s very positive.
“He’s celebrating the goals with his team-mates when he’s on the bench.
“There are a lot of positives, but he has to manage his temper a little bit. That is the challenge.”