There is a chance one or both will miss the preseason opener Thursday night in Oakland.
"We'll be very careful, obviously, but if they're ready to go we'll play them," Phillips said.
Newman was held out of both practices Saturday because of a slight groin strain. It is on the same side of his groin as an injury that slowed him last year, but Phillips said it's a different injury. He also said the rest was purely precautionary.
Newman missed all the preseason and the opener after injuring his groin in training camp last year. He later had surgery to fix a sports hernia and missed five games.
Jenkins, who is battling Orlando Scandrick for a starting job, sprained his right ankle in the morning workout.
Jenkins was covering a receiver in a full-squad drill when someone stepped on the inside of his right foot. Jenkins then twisted his leg while the foot was pinned. He was taken away to the locker room on a cart and had an MRI scan on the inside of his foot and ankle.
"It's not severe," Phillips said. "It's day-to-day, unless it changes tomorrow."
The chance of it changing is what bothers team owner Jerry Jones, who noted that high ankle sprains often don't reveal themselves until the next day. And that the injury tends to linger.
"I'm worried about it," Jones said. "We need to see on how he responds."
Jenkins and Scandrick are competing for the only starting job up for grabs. Both have played well the first 1 1/2 weeks of camp, so any missed time could put Jenkins behind.
"As well as he's done, I don't think (missing some time) will hurt him much," Phillips said.
Scandrick realizes he has a big opportunity as long as either Jenkins or Newman is out.
"I just want to grind through (fatigue) and take the little things and improve my technique and not lose my focus at all, whether Mike is out here or not," Scandrick said. "I want both those guys to get well because they need to get back out here so we can practice together."
Secondary coach Dave Campo said the competition between Jenkins and Scandrick is too close to call right now.
"I think they're both doing very well," he said. "We'll see how we do once we get into the games."
Jenkins and Scandrick are both in their second season after playing well as rookies.
Jenkins, a first-round pick, started three games and played in 14. Scandrick, a fifth-rounder, started three games and played in all 16. Regardless of who wins the starting job, the Cowboys are planning to use both on third downs.
Dallas already was without Michael Hawkins (bruised kneecap), so Scandrick and rookie Michael Hawkins were the only pure cornerbacks left.
Courtney Brown, who was drafted as a cornerback but played safety last year, has been playing cornerback in camp.
Alan Ball, who played cornerback last season, has been seeing more action at safety but moved back to cornerback for the time being.
Newman, Jenkins miss Saturday
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