The France centre forward scored the winner in Sunday's 1-0 win at home to Real Mallorca, notching only his second goal of the season to stake a claim for the striker's role in the absence of the injured Gonzalo Higuain.
Real, seeking their first domestic Cup since 1993, have said they are still looking for an extra striker in the January transfer window, while coach Jose Mourinho has also urged Benzema to work harder for his place in the side.
"What we have to do is let him work in peace," goalkeeper and captain Iker Casillas said of Benzema, who joined from Olympique Lyon for 35 million euros at the end of the 2008-09 season.
"Little by little, everything will work out well."
Left-back Marcelo added: "We have a lot of faith in him. We are happy he scored and gave us the victory."
Mourinho rested midfielders Xabi Alonso and Mesut Ozil in the first half against Mallorca, and the pair made an immediate impact after they came on at the break in a victory that kept the gap to La Liga leaders Barcelona to four points.
Ozil's Germany team-mate Sami Khedira should be available again after injury, the Portuguese coach told a news conference.
RESULT IRRELEVANT
Sevilla warmed up for Wednesday's match with a 4-1 home win over promoted Levante, which included a hat-trick for Brazil striker Luis Fabiano, his first in La Liga.
The Andalusian club have been looking to inspire their fans with a striking advertisement featuring players like captain Andres Palop, winger Jesus Navas and striker Alvaro Negredo daubing themselves with red and white war paint.
"We are extremely motivated," Ivory Coast midfielder Ndri Romaric, who also features in the advert, told reporters.
"Here at home, in front of our own people, we will play another good match and set ourselves up for return leg at the Bernabeu," winger Diego Perotti added.
Barca, the 2009 winners, are likely to be without inspirational captain Carles Puyol for the first leg of their semi-final against Almeria at the Nou Camp on Wednesday.
The shaggy-haired Spain central defender needs treatment on a left knee problem and it is unclear how long he may be sidelined, the club said on their website.
Although Barca thumped Almeria 8-0 when they visited in La Liga in November, midfielder Andres Iniesta said that result would be irrelevant come Wednesday.
"The league and the Cup are completely different," he said in an interview with As newspaper published on Monday.
"Almeria will want to make things tough for us so we have no option other than to go out and compete as best we can."
