Northampton (13) 18
Tries: Bourret, Harding, Wyles
Leicester (0) 5
Leicester reached the last four of the Anglo-Welsh Cup despite paying the price for blooding several youngsters.
Saints' France Under-21 winger Matthieu Bourret marked his home debut with the first try, with flanker Sam Harding adding another after a rolling maul.
Ian Humphreys' poor kicking throughout the game cost the Tigers several chances to get back into contention.
Paul Diggin's athleticism set up Chris Wyles for Saints' third try before Luke Abraham pulled one back for Leicester.
Northampton coach Paul Grayson on rugby league convert Stephen Myler:
"Stephen hasn't played 10 games of rugby union yet but you wouldn't know it.
"We were recommended that we looked at this player and it all happened very quickly but I'm glad it did.
"We're looking for Carlos Spencer's long-term replacement and he sees that as his opportunity."
Leicester's Pat Howard:
"I really value a game like this, so I can bring on young players.
"We get a lot of information from that sort of performance. Obviously I'm disappointed, we deserved to lose so I have no problem with that.
"We had three debutants and some fairly young players in there, but it's great we learnt a lot. I've got some hard decisions to make."
Northampton: Going; Bourret, Mallon, Kydd, Diggin; Myler, Vass; Tonga'uiha, Richmond, Barnard, Lord (capt), Gerard, Easter, Harding, Daniel Browne. Replacements: Hartley, Budgen, Damien Browne, Lewitt, Howard, Myring, Wyles.
Leicester: M Smith; A Tuilagi, Youngs, Cornwell (capt), Dodge; Humphreys, Murphy; Holford, Hickie, Young, Cullen, Hamilton, H Tuliagi, Abraham, Crane.
Replacements: Buckland, Moreno, L Deacon, Pienaar, Bemand, Hipkiss, J Murphy.