Luciano Becchio's 19th goal in 29 appearances this season salvaged a 1-1 draw for below-par Leeds against Birmingham on Saturday and kept alive the chance of another eye-catching clash with a Premier League big gun.
"We do have a huge incentive if we win," Lees told the club's official website.
"We've had a lot of great draws over the past few years. We had Man U, we've had some good ties this season and we've done well against Premier League teams.
"We have to focus on the league between now and then, but we'll have that in the back of our minds when we do go to Birmingham, because it could be a fantastic occasion at Elland Road."
Leeds beat Manchester United 1-0 at Old Trafford in the third round in 2010 and drew 2-2 at Tottenham in the following round only to lose the replay 3-1 at Elland Road.
The Yorkshire club held Arsenal to a 1-1 draw in round three the following year before losing the replay 3-1 at Elland Road and lost out to a solitary Thierry Henry goal at the Emirates Stadium at the same stage 12 months ago.