Harris missed the Guinness PRO14 victory over Edinburgh and it has now been confirmed he will spend a spell on the sidelines after suffering a PCL injury to his left knee.
However, Jackman was delighted with the way Bevington performed on his first start on home soil since the opening day clash with Benetton Rugby as the Dragons now prepare to tackle the might of Leinster on Saturday afternoon.
“Brok is out, he will miss the game and it looks like he will be out until the New Year,” said Jackman. “It doesn’t need an operation so it, but he will now rehab it.
“It is a blow, but we are really happy with Ryan Bevington. He had a slow start with a few niggles, but when we needed him on Sunday he really stepped up.
"We are also lucky to have Aaron Jarvis who covers both sides. Lloyd (Fairbrother) is going well and Leon (Brown) is back now.
“There is never a good time to get injured, but at the moment we should be able to cover him for the next period.”
Meanwhile, Jackman is yet to decide how many of his returning Wales aces to feature in the game with champions Leinster.
Wing Hallam Amos, centre Tyler Morgan and tighthead prop Leon Brown were released to feature in the win against Edinburgh while lock Cory Hill, hooker Elliot Dee and back rowers Aaron Wainwright and Ross Moriarty al returned this week.
"We need to reintegrate our internationals and it’s a great boost having them back,” said Jackman, who is hopeful Moriarty will pass all his HIA return to play protocols.
“Having Leon off the bench and Hallam and Tyler starting was great, now we have Ross, Elliot, Cory, Aaron back in the mix and they are coming back into a team that has just won rather than having massive pressure to try and lift things.
“We’ve got to be loyal to the other players – possession is nine tenths of the law. You need to have a strong case to start instead of someone else and we will have a pretty robust coaches meeting on Wednesday to finalise the team."
Dragons are back on home soil this Saturday as they face champions Leinster at Rodney Parade (kick-off 5.15pm). You can buy tickets NOW by clicking HERE
