Dillier, riding for BMC, finished the 108-mile stage (174-kilometre) from Devon to Red Deer in 3 hours, 32 minutes, 47 seconds. Moldova's Serghei Tvetcov, competing for Jelly Belly P/b Kenda, was second in the same time.
Sagan, riding for Cannondale, was 16 second behind Dillier. Sagan, the winner of the prologue time trial and first stage, took a 26-second lead over Australia's Rohan Dennis of Garmin Sharp in the overall standings.
Australia's Cadel Evans, the 2011 Tour de France champion, was fourth overall for BMC — 36 seconds behind.
The race will end Friday in Calgary.