METAIRIE, La. -- The New Orleans Saints' four-game win streak will be put to a serious test Sunday at Chicago. The team has ruled out running back Alvin Kamara and tight end Jared Cook because of injuries.

Kamara (ankle, knee) and Cook (ankle) rank second and third on the team in passing targets behind wide receiver Michael Thomas and are tied for second with two touchdowns apiece. But neither practiced this week after being injured during Sunday's game at Jacksonville.

Replacing Kamara will be veteran backup Latavius Murray, who was a No. 1 back in both Oakland and Minnesota. Veteran tight end Josh Hill will be among those filling in for Cook.

Kamara, who leads the Saints with 649 yards from scrimmage, first showed up on the injury report on Oct. 10 with an ankle injury. But he played through it before also "tweaking" his knee early against the Jaguars, according to coach Sean Payton.

The running back finished the game but was still feeling the effects this week.

Payton was asked if things like the Saints' winning streak and 5-1 record ever factor into decisions about whether to rest injured players. The coach said that's not the case here.

"I'm asked this a lot," Payton said. "[But] we take the medical, the science relative to the player being ready to play or not. And we don't factor in, 'Well, we have a bye, or we have [other circumstances].' It's, 'Is the player healthy to play?' And if he is, then we'll play him. And if he's not, then we won't.

"I think the exceptions to that might be when you get into the postseason. But I think you really try to pay attention to where the player is relative to his recovery and his injury and being smart."

The Saints signed Murray to a four-year, $14.4 million contract in free agency to both complement Kamara and be available for situations like this.

Murray, 29, has 3,836 career rushing yards, 950 career receiving yards and 35 touchdowns. He made the Pro Bowl with the Raiders with 1,066 rushing yards in 2015, then ran for a total of 1,420 yards over the past two years while splitting time in the Vikings' backfield.

"Look, he's a real good football player. And we knew when we signed him there was a vision and a role," Payton said of the 6-foot-3, 230-pounder. "He runs zone schemes well. He's smart. He knows how to block the pressure and handle some of the third-down situations."

Murray has not played a substantial role with the Saints yet, with 32 carries for 138 yards and a touchdown, plus nine receptions for 67 yards. But his touches have steadily increased each week. He had his best performance to date at Jacksonville last week; it would have looked even better if his 42-yard touchdown catch had not been nullified by a questionable holding penalty.

"I've been feeling good since Week 1, but I just think it's one of those things where the more I'm in this offense, every day in practice, the more comfortable I'm definitely gonna be," said Murray, who ran eight times for 44 yards and caught three passes for 35 yards last week. "For sure, being in this offense and continuing to get the reps has definitely helped."

Cook, who also joined the Saints this year in free agency, will be missed at a time when he was finally starting to find a groove. Over the past two weeks, he caught a total of seven passes for 78 yards with his first two touchdowns of the season.

The Saints ruled out quarterback Drew Brees for the fifth straight game with his thumb injury -- though he is on the mend after starting to throw a regulation-sized football again last week. They also ruled out wide receiver Tre'Quan Smith (ankle) and defensive end Trey Hendrickson (neck).