Tomsula seeks cure for 49ers’ big-play woes on defense

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At one point during 49ers head coach Jim Tomsula’s news conference Monday, he was asked about the similarities between Steelers quarterback Ben Roethlisberger and Arizona’s Carson Palmer.

They’re both strong-armed and eager to throw deep - so could the 49ers apply any lessons from Sunday’s lopsided loss in Pittsburgh to next Sunday’s game against the Cardinals?

Tomsula reduced his answer to its simplest form.

“We’ve got to make sure they’re not behind us,” he said. “We don’t want to give up the big play.”

No kidding.

The 49ers allowed six plays of 28 yards or longer in their 43-18 defeat to the Steelers. Five of those plays came on third down, as San Francisco crowded “the box” a bit in an effort to prevent Pittsburgh from picking up the first down.

Roethlisberger promptly went deep, time after relentless time.

“Our biggest struggle was third-and-medium,” Tomsula said Monday. “You’re protecting the sticks. One play was a bad angle (by a 49ers defensive back), but their guys made good plays and we didn’t make the plays.”

The Cardinals will pose a similarly stout challenge. They breezed to a 48-23 win over the Bears on Sunday, with Palmer throwing for 185 yards and four touchdowns.

Pittsburgh Steelers wide receiver Antonio Brown (84) smiles after making a touchdown catch past San Francisco 49ers cornerback Kenneth Acker (20) in an NFL football game, Sunday, Sept. 20, 2015, in Pittsburgh. (AP Photo/Gene J. Puskar) less Pittsburgh Steelers wide receiver Antonio Brown (84) smiles after making a touchdown catch past San Francisco 49ers cornerback Kenneth Acker (20) in an NFL football game, Sunday, Sept. 20, 2015, in Pittsburgh. ... more Photo: Gene J. Puskar, Associated Press Photo: Gene J. Puskar, Associated Press Image 1 of / 1 Caption Close Tomsula seeks cure for 49ers’ big-play woes on defense 1 / 1 Back to Gallery

Arizona leads the NFL in scoring, averaging 39.5 points per game.

Tomsula didn’t offer much insight as to what caused the 49ers’ repeated breakdowns Sunday, or whether their youth on defense might have played a role. He sidestepped a question about the tepid pass rush on Roethlisberger, saying of all the big plays, “We’re not sitting up here assigning blame.”

Later in his news conference, Tomsula was asked about the 49ers’ biggest play, a 75-yard touchdown pass from Colin Kaepernick to Torrey Smith. In a rare moment, Tomsula ducked the chance to offer positive words about his team.

“Nothing was glowingly beautiful yesterday,” he said.

Or, as Smith said succinctly Monday, “They definitely whipped up on us. There’s no way around it.”

Injury updates: Tomsula doesn’t expect any of the 49ers’ injured players to miss time because of injuries: Smith (leg contusion), running back Carlos Hyde (who passed a concussion test and also had a leg contusion) and tight end Vance McDonald (contusion below his knee; X-rays were negative).

Wide receiver/punt returner Bruce Ellington missed Sunday’s game with an ankle injury, though Tomsula said Ellington thought he could have played. “We just made the decision not to push it,” Tomsula said.

Ellington will continue to receive treatment in advance of this week’s game in Arizona.

Ron Kroichick is a San Francisco Chronicle staff writer. E-mail: rkroichick@sfchronicle.com Twitter: @ronkroichick