The O's are back in league action when they welcome Chesterfield to the Breyer Group Stadium (3pm kick-off) on Saturday.
The National League leaders fell to only their second league defeat of the season two weeks ago but responded well in the FA Trophy last week with a 4-0 win over Beaconsfield Town in E10.
The O's made seven changes and George Elokobi, who made his first appearance since August, opened the scoring in the 17th minute. James Brophy doubled the advantage just after half-time before goals by Craig Clay and Dale Gorman wrapped up the win and confirmed a trip to Wrexham AFC in the Second Round.
Martin Allen's side come into the game having not tasted defeat in 14 matches after a remarkable run of form that saw them draw nine league matches in a row before beating high-flyers Salford City.
The Spireites took the lead through Alex Kiwomya in the 2nd minute before the former-Doncaster Rovers midfielder doubled his tally in the 59th minute.
The side, who are currently sat in 20th position, continued their recent good form with a 5-1 win over Basford United in the FA Trophy last week.
The O's will be without James Dayton and Charlie Grainger, who are long-term absentees, but should be bolstered by the return of Charlie Lee and Myles Judd to contention.
Chesterfield will be without defender Bradley Barry, who is out with a head injury, but Martin Allen has assured supporters that Curtis Weston is "200% fit"
Adrian Quelch is the official for tomorrow's match, assisted by Oliver Jackson and Dan Bonneywell. The Christchurch-based official has given 41 yellow cards this season with two red cards. He took charge of the O's draws to Ebbsfleet United and Hartlepool United, sending off Joe Widdowson in the latter.
Can’t make the game? Follow live updates through the official Twitter feed, or listen to audio commentary from Dave Victor on Ozone.
Audio commentary will be available through the match centre which will appear at the top of the leytonorient.com homepage, with commentary starting 30 minutes before kick-off.
Match report and reaction following the game will appear on leytonorient.com.