Prior missed the last two City games with a slight neck injury. He last played at home against Plymouth when he was booed onto the pitch by a small element of the City crowd as he came on as a late substitute.
Lennie is happy to play Prior and thinks it may be better for him to start an away game
"I think it's better for Prior to make his first step back into the team away from home" Lennie told the Echo.
"I know he could cope if it was at Ninian Park, but I think on this occasion it's better he gets the first game under his belt at Brentford.
"Fans will say what they want to say, their pay their money and that's that. But on this issue, it will not do the player any harm starting the game away from home.
"Spencer has been out of the team over the last couple of weeks, but that has given him a chance to get his throughts together. He's got an unexpected call up to the starting line up and it's a great, and probably earlier, oportunity than he thought he might have. It's up to him to grab the chance with both hands.
"Spencer was upset that he got booed even before he went on as a substitute against Plymouth, and was even more upset at the reaction after the free kick, which led to the equaliser.
He has been quite brave going public about what he thought of the reaction, and now he has got to get out there and do it. The best thing he and the team can do is keep a clean shhet, and if we don't score down the other end, then it's important that the defence do their job.
"I have had many chats with Spencer, he likes the area and I feel he really wants to stay here. Graham Kavanagh and Rhys Weston both came through periods of critisism, and I'll be very surprised if Spencer does not rise to the challenge and show what he is capable of".
Prior comes into the team becuase of injury to Rhys Weston and Steve Jenkins. Lennie will play Chris Barker at left back and slot Prior alongside Scott Young in central defence. Gary Croft will move to right back.
It's thought Lennie will keep Boland / Bonner / Kav in midfield with Mahon starting the game if Gavin Gordon is not passed fit. Thorne and Earnshaw both play. The injuries also mean a chance of a place on the bench for Layton Maxwell and Leo FW.
Kick off tonight is at 7:45pm. There will be chat room coverage and updates on Radio Wales.