Dennis is suffering from sinusitis which has ruled him out of the eight-stage race across France, news which has left him downhearted.
"I really wanted to win the time trial on Sunday so it is disappointing to not be lining up. I've felt the illness lingering a bit in the past few days but today it has really hit me and we don't have enough days ahead of Sunday for a proper recovery.
"At the end of the day my health is the priority and I'm focused on recovering well and lining up at my next race," Dennis said.
BMC doctor, Dr. Daniele Zaccaria said it would not affect Dennis' long term goals.
"With antibiotics and some solid rest he should be back on the bike within the next five days and we don't expect this illness to affect his racing program beyond Paris-Nice,' he said.
Peter Velits will replace Dennis, and with Richie Porte lining up in Paris, BMC still has a strong team.
BMC team for Paris-Nice: Marcus Burghardt, Philippe Gilbert, Ben Hermans, Amaël Moinard, Richie Porte, Michael Schär, Peter Velits, Danilo Wyss.
SBS2 will broadcast all stages of Paris-Nice from Sunday, 6 March to Sunday 13 March and online at Cycling Central at the following times:
Sunday 6 March: 2330 – 0100 AEDT
Monday 7 March: 0115 – 0300 AEDT
Tuesday 8 March 0150 – 0325 AEDT
Wednesday 9 March: 0150 – 0325 AEDT
Thursday 10 March: 0115 – 0250 AEDT
Friday 11 March: 0115 – 0250 AEDT
Saturday 12 March: 0125 – 0310 AEDT
Sunday 13 March: 2340 – 0110 AEDT