Andrew Trimble also returns to the starting team after missing the last two games through injury but Stephen Ferris continues to be ruled out with a knee problem.
Rory Best takes over the captaincy from Johann Muller on his return to the starting XV. He played 15 minutes against Glasgow last week after returning from 6 Nations duty and will start alongside Botha and Tom Court in an all-international front row. In the back row Willie Fallon gains a start at openside flank in place of Chris Henry who drops to the bench.
The backline has also been re-shuffled as Ruan Pienaar moves back to scrum half to allow Humphreys to take the No10 jersey. Adam D'Arcy comes in at fullback as Simon Danielli moves to the wing and Craig Gilroy starts on the bench. The other wing berth is occupied by Trimble who has replaced 20 year old Conor Gaston.
Ulster are on a run of five straight wins, with three of those coming courtesy of last-gasp kicks. The last time Ulster won six in a row they went on to win the league in 2005/06.
They currently occupy third position in the table and will face a stern test against their fellow play-off contenders. A win tonight is not only important for their Magners League challenge but they will be hoping for victory and an improved performance ahead of next week's Heineken Cup quarter final against Northampton.
Ulster Team v Scarlets (Magners League, Ravenhill, Friday 1st April, kick-off 7.05pm)
(15-9):A D'Arcy; A Trimble, N Spence, P Wallace, S Danielli; I Humphreys, R Pienaar;
(1-8): T Court, R Best (capt), BJ Botha, J Muller, D Tuohy, R Diack, W Faloon, P Wannenburg;
Replacements (16-23): A Kyriacou, P McAllister, D Fitzpatrick, T Barker, C Henry, P Marshall, I Whitten, C Gilroy.
Ulster Rugby would advise supporters coming to the game (gates open 5.30pm) to avoid parking in the immediate vicinity of the Ravenhill Grounds and that the following roads are only accessible for residents and closed to everyone else:
1. Onslow Parade
2. Ravenhill Park
3. Ravenhill Park Gardens
There will also be parking restrictions in place in the Castlereagh area (Mount Merrion Avenue). Supporters are encouraged to make use of the Park 'n' Ride facilities at Pirrie Park and along Montgomery Road.
Your co-operation is gratefully appreciated.