"Brendon (BJ) has been training with the Sharks for the last few weeks so I have no concerns over his fitness levels, he has impressed us all at training this week and I am delighted to name him in the side," Williams admitted.
"It's important to hit the ground running and I feel we have picked a strong side for the first game.
"We're ready for the Scarlets. I have mentioned this week in the media that we have had selection issues in that we have a great squad to choose from - that is something I am really pleased about.
"The Scarlets are a good side and have recruited well over the summer, they will be keen to lay down the law at Ravenhill as we meet them again in the Heineken Cup in December.
"But we are determined to get our season off to a good start and build that confidence in the team up."
The front row is transformed with stalwart Justin Fitzpatrick named at loosehead, team captain Rory Best at hooker and Botha on the tighthead side.
In the second row Italian lock Carlo Del Fava partners new recruit Ed O'Donoghue. The back row sees recent signing Robbie Diack return at number 8 with Matt McCullough and Kieron Dawson named as the two flankers.
Isaac Boss and Paddy Wallace have been named as the half-back pairing with former Australia 'A' international Clinton Schifcofske positioned at full-back.
Ireland ace Andrew Trimble starts on the right wing with Fijian international Timoci Nagusa taking on the left wing berth. The centre pairing of Scotland's Rob Dewey and Ireland Sevens star Darren Cave could cause the Scarlets a number of problems.
ULSTER (v Llanelli Scarlets): Clinton Schifcofske; Andrew Trimble, Darren Cave, Rob Dewey, Timoci Nagusa; Paddy Wallace, lsaac Boss; Justin Fitzpatrick, Rory Best (capt), BJ Botha, Carlo Del Fava, Ed O'Donoghue, Matt McCullough, Kieron Dawson, Robbie Diack.
Replacements: Nigel Brady, Tom Court, Ryan Caldwell, David Pollock, Cillian Willis, Niall O'Connor, Bryn Cunningham.