Howells has put fullback Kevin Morgan, centre Gareth Thomas, Samoan scrum-half Sililo Martens, prop Gethin Jenkins and lock Rob Sidoli straight back into the starting lineup, while Mefin Davies, Brent Cockbain and Ceri Sweeney warm the bench.
Centre Sonny Parker and scrum-half Gareth Cooper are still feeling the effects of Cup injuries and miss the match to prepare for the Heineken Cup kick-off in 10 days.
Warriors skipper Gareth Thomas, named in the World Cup squad as a winger but who filled in at fullback for the crucial matches against New Zealand and England, will start at outside centre.
A win will have the fifth-placed Warriors pushing for a top-three spot in the Celtic League ladder, but a loss will have them struggling to keep up with pace-setters Ulster and the Llanelli Scarlets.
Celtic Warriors: K Morgan; D James, G Thomas (capt), J Bryant, A Havili; N Jenkins, S Martens; G Jenkins, M Rees, C Horsman, D Jones, R Sidoli, M Molitika, C Harris, R Parkes.
Replacements: M Davies, C Loader, B Cockbain, N Kelly, P John, C Sweeney, G Wyatt.