Bad news became the worst news — another torn pectoral muscle for Al Horford.

The Hawks center will be lost, likely for the season, after suffering a complete tear of his right pectoral muscle. An MRI and examination Friday revealed the severity of the injury sustained the previous night against the Cavaliers.

The Hawks offered no timetable for Horford’s return. However, he missed most of the 2011-12 season with a tear of his left pectoral muscle. He suffered that injury 11 games into the season and returned, not at 100 percent, for the playoffs. This injury comes 29 games into the season.

“We will work with Al and complete our due diligence to determine the next best steps for him,” general manager Danny Ferry said in a statement. “Injuries are part of the challenge of an NBA season.”

Horford was examined by Dr. Michael Bernot of Peachtree Orthopaedics in Atlanta on Friday for the diagnosis. The Hawks said Horford will be out indefinitely, and his status will be updated at the appropriate time.

Later Friday he tweeted: “A bump on the road with this injury, but I will focus to get back more focus and better!”

Horford left with 1:35 remaining in the first overtime of the Hawks’ double-overtime victory Thursday. He was injured when he got tangled with the Cavaliers’ Anderson Varejao. The injury initially was described as a right shoulder injury. Horford was not available to speak to reporters following the game.

The injury is a huge blow for the Hawks, who with a 16-13 record rank third in the Eastern Conference standings. Horford leads the team in points (18.6) and rebounds (8.4). The points-per-game total is the highest of his six-plus seasons.

The Hawks have veteran Elton Brand and Gustavo Ayon, who has missed 14 games because of injury, to initially fill the void left by Horford. The Hawks inquired about disgruntled Rockets center Omer Asik earlier this month. However, the reported asking price involved power forward Paul Millsap, a player the Hawks are unlikely to part with now.

“The idea is we have a goal and a system that we play and we trust,” coach Mike Budenholzer said Friday afternoon before news of the exact injury. “Obviously, Al is one of our best players and invaluable to us, but there won’t be a huge, significant change, and we will have a comfort level defensively and offensively. It doesn’t matter who is there. As best as possible, we’ll be able to function without Al.”

The Hawks play host to the Bobcats on Saturday in the first game without Horford.

Horford, a two-time All-Star, returned from the previous torn pectoral muscle to play three games of the Hawks’ playoff series with the Celtics. He averaged 15.3 points and 8.3 rebounds in the series, which the Hawks lost in six games.

Also, in the game against the Cavaliers, the Hawks lost DeMarre Carroll to a right thumb sprain in the fourth quarter. Carroll was injured fighting through a screen set by the Cavaliers’ Tyler Zeller. The forward had his thumb X-rayed in Cleveland on Thursday and in Atlanta on Friday. The results were negative for a fracture or ligament damage, and Carroll is listed as day-to-day.

John Jenkins, who missed Thursday’s game with nerve pain in his left leg, remains out. Jenkins, his agent and team management are discussing a course of action to resolve the back-related issue that has plagued the guard since the offseason.