Henshaw sustained a flexor strain in Ireland’s victory over Australia last week and has failed to recover, but international teammates Kieran Marmion and Rodney Ah You are named in Pat Lam’s starting side.
Jack Carty returns to partner Marmion, while up front hooker Tom McCartney makes his first start, for the injured Jason Harris-Wright. Andrew Browne replaces Mick Kearney in the second row and Eoin McKeon comes in for Willie Faloon at openside.
Lam said: “It’s great to bring back the experience of Kieran and Rodney for what is undoubtedly a big game for us. It’s unfortunate Robbie wasn’t fully ready to come back in, but it’s important he is given the time to recover ahead of a very busy and crucial block of game for us.”
Both sides are unbeaten at home this season, with Connacht ahead of the Welsh outfit by a point in the coveted sixth qualifying spot.
It is a position Connacht do not want to relinquish this evening, particularly with Scarlets missing a host of internationals.
M Muliaina, D Poolman, B Aki, D McSharry, M Healy, J Carty, K Marmion, D Buckley, T McCartney, R Ah You, Q Roux, A Browne, J Muldoon (c), E McKeon, G Naoupu.
Replacements: D Heffernan, R Loughney, F Bealham, M Kearney, W Faloon, J Cooney, C Ronaldson, D Leader.
S Evans, H Robinson, M Tagicakibau, R King, K Phillips, S Shingler, A Davies, P John, K Myhill, P Edwards, G Earle, J Snyman, A Shingler, J Davies, J Barclay (c).
Replacements: R Elias, W Jones, J Adriaanse, L Rawlins, R Pitman, K Hardy, J Lewis, G Owen