Denver CB Tracy Porter’s bruised knee contributed to him getting burned on two long touchdown passes during the loss to Houston on Sunday. (US Presswire)

It was a bruised knee that kept Denver Broncos CB Tracy Porter sidelined for the final two and a half quarters on Sunday -- but it was an injury he didn't initially sustain in the game.

"It's an old injury that got re-tweaked," Broncos coach John Fox said. "He either hit the ground real hard, or something hit the knee hard."

Porter gave up two long touchdown passes in his brief action Sunday: a 60-yarder to Houston's Andre Johnson and a 52-yarder to Kevin Walter. But Fox said that Porter should have had safety help on Johnson's score. On that play, Rahim Moore bit on a play-action fake, and Mike Adams arrived too late to have any impact on coverage.

Porter had tighter coverage on Walter, but was beaten by what Fox called a "great throw" from Texans QB Matt Schaub.

The fifth-year CB is considered "day-to-day." Chris Harris replaced him on Sunday and the Broncos changed their coverage going forward, using Champ Bailey as a roving defender who was assigned exclusively to Johnson, who didn't have a catch against Bailey until grabbing a 12-yard pass on third-and-5 with 2:49 remaining.

Kuper Update: Fox said he plans to have a "look-see" at Chris Kuper this week, as the starting right guard continues his recovery from a fractured forearm, but reminded reporters that Kuper hadn't practiced "in some time."

Kuper has been sidelined since Aug. 14 because of the injury. The Broncos hoped to have him back by the end of September, but they might choose to ease Kuper back into playing shape, which might delay his return by a week.

The fill-in for Kuper, Manny Ramirez, has seen his struggles multiply exponentially in recent weeks and was at least partially responsible for all three sacks the Broncos allowed Sunday.

Other injuries: Backup LB Nate Irving is going through the requisite post-concussion protocol, Fox said. He added the groin injury to TE Jacob Tamme and WR Matt Willis' hamstring injury are both "strains," and that RB Willis McGahee's rib injury is to his cartilage. All are considered "day-to-day."

For up-to-the-minute Broncos updates, follow Andrew Mason on Twitter at @CBSBroncos and @MaseDenver.