The midfielder was substituted at half-time in last Saturday’s 3-1 away defeat to Nottingham Forest after a reoccurrence of a troublesome thigh injury in his comeback appearance.
Trotter looks set for a further two-to-three-week spell on the sidelines with the same thigh injury that had ruled the midfielder out for two weeks prior to his return at the City Ground.
The Lions will also be without centre-half Shane Lowry as he continues his recovery from an ankle injury sustained a fortnight ago in the 2-1 home defeat to Reading.
Left-back Tony Craig is also a doubt for the Lions with a knock and will be assessed before the game tomorrow. Leading marksman Darius Henderson will be pushing for a recall following his goal against Forest last Saturday.
Goalkeeper Steve Mildenhall remains unavailable with an ankle injury, which has forced manager Kenny Jackett to strengthen his hand via the loan market, with Maik Taylor joining from Leeds United on Monday.
The 40 year-old looks set to be included in tomorrow’s match-day squad and could be in line for his Lions debut between the sticks against the Saints, although it is expected that Taylor will be named among the substitutes, in place of youngster Ryan Allsop.
Tamika Mkandawire, although unavailable for tomorrow’s fixture, could be available before the season’s conclusion as he steps up his recovery from cartilage damage in his knee. However, midfielder Therry Racon has been ruled out for the remainder of the season with an ankle injury.
Southampton travel to the The Den on Saturday with the ability to call upon the majority of their squad after the return to fitness of several players in the run-up to tomorrow’s fixture.
Midfielder Richard Chaplow and former Millwall loanee Jason Puncheon will be pushing for recalls to the match-day squad after missing last Saturday’s home win against Barnsley.
Fit-again centre-back Radhi Jaidi and Tottenham loanee Yago Falque are both pushing for recalls to the first-team picture following reserve appearances in midweek.
Frontmen David Connolly and Tadanari Lee both sustained knocks during last Saturday’s 2-0 home win to Barnsley although the duo are expected to be fit for selection.