The Italy international started in the 1-1 draw with Fulham last weekend, but he was withdrawn midway through the second half after sustaining a slight thigh problem, making him a minor doubt for the contest against his former club Chelsea.
West Ham are hopeful that Emerson will recover in time, but his potential absence could see either Aaron Cresswell or Aaron Wan-Bissaka handed a start at left-back.
The Hammers' only other injury concern is with summer signing Niclas Fullkrug, who missed the draw with Fulham as he is nursing an Achilles injury - the German striker is set to be assessed ahead of kickoff.
Michail Antonio has started in all of West Ham's first four Premier League games this term, but he has struggled to make the desired impact up front and was replaced at half time against Fulham.
Substitute Danny Ings ended that match as West Ham's striker and after scored a dramatic 95th-minute equaliser, Lopetegui may consider handing the 32-year-old a start on Saturday, although Jarrod Bowen is another option to lead the line.
Lucas Paqueta began as a substitute last time out, but he could be recalled at the expense of Tomas Soucek to start against Chelsea, potentially linking up with Crysencio Summerville and Mohammed Kudus in the final third.
Edson Alvarez and Guido Rodriguez may retain their places in deep-lying midfield roles, while Max Kilman is expected to continue at centre-back alongside either Konstantinos Mavropanos or Jean-Clair Todibo, the latter of whom is pushing to start his first Premier League game.
West Ham United possible starting lineup: Areola; Wan-Bisakka, Mavropanos, Kilman, Emerson; Alvarez, Rodriguez; Kudus, Paqueta, Summerville; Bowen