The move comes just a week after the Latics announced the capture of Arouna Kone from Levante in La Liga.
Kone's arrival along with the return of Mauro Boselli from his loan period with Estudiantes appears to have spelled the end for Sammon who won the hearts of Latics fans with his combative displays and that goal against West Ham.
Sammon was a firm fans favourite despite struggling to prove his worth at the very top. The switch to Derby is likely to benefit both parties with the powerful Irish man likely to have a big impact at Championship level.
Sammon joined the Latics for a fee believed to be in the region of £600,000 from Scottish Premier League team Kilmarnock and it is believed that around £500,000 of that fee has been recouped in the switch the Derby.
Without doubt everyone connected with Wgian Athletic will wish Connor all the best for the future and hopefully we will meet again in the not so distant future after the Irishman's goals have fired County to the Premier League.
Good luck Connor.