West Brom's Jerome Thomas has been ruled out after twisting his ankle during the 1-0 win over Sunderland at the weekend.
Ishmael Miller and defender Joe Mattock are also on the sidelines, and new signing Somen Tchoyi will not play a part as he is lacking match fitness.
MATCH FACTS
Head-to-head
• Their most recent meeting was in the League Cup. Albion won the first round tie 3-0 at Brisbane Road in August 2006.
• West Brom have prevailed on 18 of 32 occasions when the sides have met, Orient have won six, and eight have been drawn.
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Leyton Orient
• Leyton Orient, who put out fellow League One side Swindon in the first round, have qualified for the second round three times in the last four years.
• But the 1963 quarter-finalists have not appeared in round three since 1991.
• Russell Slade's side have scored in each of their four league and cup games this season, but the Carling Cup success over Swindon is their only victory so far.
• Adam Chambers was a West Brom trainee and he is in line to make his 250th club career appearance.
West Brom
• West Brom reached the third round last season where they were knocked out by Arsenal.
• The season before, when they were a Premier League club, League One side Hartlepool knocked them out in the second round.
• The Baggies won the League Cup in 1966, and have been runners-up twice since.
• Albion's only previous away game this season saw them trounced 6-0 by Chelsea.
• Nicky Shorey was a Leyton Orient trainee.
Source: BBC Sport
Source: BBC Sport