Midfielder Hammond completed his switch from Colchester for a reported £400,000 fee earlier this week and centre-half Trotman has since arrived from Preston on a loan deal until January.
Saints boss Alan Pardew will hand a late fitness test to veteran right-back Graeme Murty, who missed Tuesday night's defeat at Swindon with a dead leg and remains a doubt.
Midfielder Joseph Mills is still on the sidelines with a hamstring injury and young forward Kayne McLaggon is continuing his recovery from a ruptured Achilles.
Pardew will again choose between Matt Paterson, Grzegorz Rasiak and Marek Saganowski to partner £1million striker Rickie Lambert in attack.
