The Saddlers have home advantage in the second round tie against a team they drew 0-0 with away two weeks ago.
But Carlisle are likely to have 12-goal striker Kristian Dennis back from injury - the 32-year-old was on the bench for the league game but scored two as Carlisle beat Salford City 4-1 away last weekend.
Flynn has made no secret of his own desire for a cup run and to make some money for the cub by drawing a big gun in the third round but thinks Carlisle will prove tough opponents.
He said: “They are up there in the play off places but both team’s focus this weekend will be on the cup and getting in the draw for Monday.
“There isn’t much between us and one mistake or chance could prove crucial.”
Match Preview – Page 46