The Cardinals have only allowed one sack this year but face a tough Rams' defensive line on Sunday.

Mike Iupati practiced in a limited capacity on Wednesday, and there is hope the Pro Bowl guard can make his Cardinals debut on Sunday against the Rams.

If it happens, the timing couldn't be better.

The Cardinals have given up only one sack through three games, the lowest total in the league and one of many reasons for an undefeated start to the year. But they have yet to roll out all five projected starters due to Iupati's knee injury and right tackle Bobby Massie's two-game suspension, and could need all hands on deck on Sunday against the Rams.

While St. Louis has struggled to score points during its 1-2 start, the defensive line has been as advertised. The Rams are tied with the Patriots for the league-lead in sacks with 13, and knocked Steelers quarterback Ben Roethlisberger from last week's contest with a knee injury.

The Cardinals offense hopes to keep rolling this week, but can only do that by keeping quarterback Carson Palmer upright.

"It's a heightened urgency," left tackle Jared Veldheer said. "It's some of the very best players in the world on that D-line. To me, that's fun. That's the biggest challenge you've got, and to be able to go to work and prepare makes that week kind of special."

The Rams have several veteran stars including Robert Quinn, Chris Long and Nick Fairley, but the jewel is a player in just his second year. Aaron Donald made the Pro Bowl as a rookie and already has an argument as the best defensive tackle in the NFL.

Donald has 18 tackles and 3½ sacks this season, and is equally formidable against the run and the pass. The Cardinals haven't faced anyone close to his quality in the first three games, and it will be a challenge for the interior of the offensive line.

"He's always making plays," guard Jonathan Cooper said. "People underestimate him because of his stature. He's a shorter guy, but he's quick off the ball. He's strong and explosive. He has moves for days."

Coach Bruce Arians said Iupati made it through the whole practice and looked "really good," but wasn't ready to handicap his chance of starting.

"We will wait and see," Arians said. "It's still a long ways away. He will have to tell me he wants to play."

A PICK PARTY ALL AROUND IN THE SECONDARY

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Cardinals lead the league with seven interceptions, all of which have come from the secondary. Safety Tyrann Mathieu is the lone player with two, and he's one of three players – joined by safety Tony Jefferson and cornerback Justin Bethel – with interception returns for touchdowns.

Safety Rashad Johnson, cornerback Jerraud Powers and cornerback Patrick Peterson are the others with interceptions. The balance of playmakers doesn't surprise Johnson.

"We knew it was going to be like this because of the competition we had in training camp," he said. "We didn't know who was going to start, how it was going to work out. And we're still rotating guys throughout the game because we have so many guys who can get it done."

ELLINGTON MAKING PROGRESS, HOPES TO PLAY AGAINST RAMS

Running back Andre Ellington (knee) was limited in practice Wednesday and said he wants to get back on the field Sunday, but also has to be smart about it. Coach Bruce Arians called his availability for the Rams game a "50-50" proposition.

"He can go straight ahead real fast as always," Arians said. "It's just the turning and stopping a little bit."

Ellington said "it's just getting back in the groove of things. For the most part, I feel pretty good."

Wide receiver J.J. Nelson (shoulder) didn't practice Wednesday and isn't expected to play this week. Wide receiver John Brown (shoulder) and linebacker Alex Okafor (shoulder) were limited.

For the Rams, safety Maurice Alexander (groin), wide receiver Kenny Britt (shoulder), linebacker James Laurinaitis (not-injury-related), running back Chase Reynolds (knee) and defensive end Eugene Sims (knee) did not practice.