With the first day of the match having been entirely lost to rain, Northants needed early wickets after captain Alex Wakeley exercised the away team's right to bowl first at the Fischer County Ground.
The visitors have to win the match to retain a chance of promotion, butand suffered an immediate blow when leading wicket-taker Rory Kleinveldt pulled up with an injury after bowling just eight deliveries.
With the ball swinging just enough in the humid conditions, however, Sanderson and Gleeson made light of Kleinveldt's enforced absence. Sanderson had both Michael Carberry and Ned Eckersley plumb leg before wicket before Gleeson produced a bouncing, seaming delivery which Sam Evans, making his championship debut for the Foxes, inside-edged to the wicket-keeper.
Gleeson then accounted for Mark Cosgrove, the Leicestershire captain inside-edging an attempted drive at a full delivery on to his off-stump, and Aadil Ali became Sanderson's third leg-before victim before Gleeson first had Lewis Hill leg before, and then bowled Neil Dexter with an unplayable delivery which left the South African off the pitch.
Raine, dropped by Richard Levi at second slip on 15 off Gleeson, and Chappell – who should have been easily run out on 5, only for wicket-keeper David Murphy to fumble a simple take – then counter-attacked to some effect until shortly before lunch, when Chappell edged a Sanderson outswinger to second slip.