Brisbane's win over the Bulldogs has been soured by a knee injury to captain Alex Glenn.
Glenn sustained the injury in the second half and is set to go for scans on a suspected medial cruciate ligament injury.
"He is not real good," Seibold said after the 26-8 win over the Bulldogs.
"It's his MCL (medial cruciate ligament) so he will be in a brace and miss a period of footy. He won't need an operation but he will get a scan tomorrow. They are not concerned about his ACL.
Glenn will likely be able to return before the end of the season.
Winger turned second-rower Corey Oates excelled as Glenn's back-row partner, scoring a try and standing up when the skipper went down to lead the Broncos to their third win of the season.
"I enjoyed what he did tonight. I probably poked Oatesy a couple of weeks ago when I dropped him from the wing," Seibold said.
"It was probably a tough decision, but I thought he was real good in the back row. He ran some really strong lines and defensively he was very good."