Coach Pat Lam has made only one change to his starting XV, with Ultan Dillane coming in for lock Ali Muldowney, who moves to the bench.
The 22-years-old, who trained with the Ireland camp this week, makes his sixth start this season since making his debut last season as an Academy player.
With both sides coming off the back of a poor run of results, it is expected to be a hugely competitive affair. The odds favour the home side, but Connacht, who have not won in Llanelli since 2004, will be keen to add another milestone to their season, and maintain their push for Champions Cup rugby.
Lam says this round 12 fixture will not make or break Connacht’s season, but “it will determine a lot going forward”.
“It is two good teams, both of which are coming off a run of losses.
“We are sitting first and third with two points between us, so it has importance in the context of where everyone sits, and it is important we focus on the process to give ourselves a chance.
“They have lost the last four games as well, so no doubt about it they will be up for the game. They have quality players, they have a big squad and are well coached.”
Lam says there were many positives in their disappointing 13-0 defeat to Leinster, but they will be looking to improve tomorrow.
“After a solid week’s training, we go to Wales with confidence, knowing that if we add clinical execution to the work ethic already shown we’ll have every chance.”
The hosts have also faced a nightmare run of injuries in recent weeks, but welcome back Scottish flanker John Barclay and No 8 Rory Pitman to bolster their back row, while centre Regan King returns to the starting XV with Gareth Owen out injured.
The Scarlets, despite having lost seven out of their last nine matches in all competitions, still lead the table, but with just 13 points separating the top from ninth-placed Cardiff, every game now matters at this half-way stage.
M Collins; S Evans, R King, H Parkes, DTH van der Merwe; A Thomas, A Davies; R Evans, K Owens (capt), S Lee, T Price, L Rawlins, A Shingler, J Barclay, M Allen.
R Elias, P John, R Jones, M Paulino, R Pitman, R Williams, S Shingler, S Hughes.
T O’Halloran; N Adeolokun, B Aki, C Ronaldson, M Healy, J Carty, K Marmion; F Bealham, T McCartney, N White, U Dillane, A Browne, J Muldoon (capt), J Heenan, E Masterson.
D Heffernan, R Loughney, R Ah You, A Muldowney, S O’Brien, I Porter, AJ MacGinty, R Parata.