Not 24 hours after their big victory over the Chiefs on Sunday night, the Broncos on Monday were talking losses — to injury, that is.

Broncos safety Rahim Moore is expected to miss several weeks after being diagnosed with lateral compartment syndrome, the most serious injury by far of the night.

Moore left Sunday night’s game against the Chiefs with pain in his lower left leg about halfway through the second quarter. He was diagnosed in the middle of the night, when he experienced more pain and was hospitalized, Broncos interim coach Jack Del Rio said. He then had surgery early Monday morning.

Compartment syndrome occurs when a muscle — which is essentially in a compartment between two fasciae, the connective tissue that surrounds muscles — begins to swell. Swelling continues and continues, eventually restricting blood flow to the muscle, which can lead to nerve damage.

Surgeons diagnose the syndrome by inserting a needle into the muscle to check the pressure. Surgery is performed to trim away at the fasciae and give space for the muscle to swell.

The Broncos are considering placing Moore on the injured reserve list, sources said, although it’s still uncertain how long Moore will be sidelined. Much depends on the length the syndrome goes undetected; the longer it goes, the more the nerve damage, the longer the recovery.

“It’s a new one for me,” said Del Rio, who added that he hadn’t heard of the syndrome before.

“It’s one of those freakish things that can occur.”

Before exiting the game, Moore logged two solo tackles and defended a pass. Mike Adams, who started at safety for much of the 2012 season, entered the game in Moore’s place and likely will assume the bulk of his role in his absence.

After making a name for himself by blowing coverage on the play that ushered the Broncos out of the playoffs last season, Moore has been having a resurgence in 2013. He started each of the Broncos’ first 10 games and has 44 tackles.

A third-year player from UCLA, Moore was on pace to come close to matching his season totals from 2012, when he emerged as a full-time starter for the Broncos.

The two other players injured Sunday had slightly better prognoses. Receiver Wes Welker, who was diagnosed with a concussion, will go through the NFL’s protocol this week to determine when he can return. Tight end Julius Thomas has a knee strain and is day-to-day.

Welker did briefly return to the game after initially being evaluated for a concussion on Sunday night, though the Broncos did follow the league’s protocol.

“He had symptoms that flared up or came up, and then he was replaced,” Del Rio said. “The first concern, obviously, is to make sure he’s ready to return when the doctors give the green light. If we’re told that he’s able to go, then he’ll go.”

In better news among the ranks of the Broncos’ ailing, coach John Fox was able to video chat with his team Monday morning.

“He was able to visit with the team, take questions,” Del Rio said. “He looked great and was full of energy. The players, coaches, everybody got a lift seeing him and seeing his spirit, how fired up he was to be able to talk to everybody.”

Joan Niesen: jniesen@denverpost.com or twitter.com/joanniesen

Mike Klis: mklis@denverpost.com or twitter.com/mikeklis