Sexton, who had recovered from the hamstring injury that had kept him out and was named in the starting XV earlier today, went over on his foot in training.
A scan has confirmed that he has torn a tendon in his left foot and is therefore ruled out this weekend.
Paddy Jackson will start the game, earning his 3rd cap. Ian Madigan, who made his debut against France last weekend,comes in to the replacements.
The Ireland Team to play Italy on Saturday 16th March 2013 in Stadio Olimpico, Rome in the RBS 6 Nations Championship, K.O. 2.30pm (local time), is:
(Player/club/province/international caps):
15 – Rob Kearney (UCD/Leinster/45)
14 – Craig Gilroy (Dungannon/Ulster/4)
13 – Brian O’Driscoll (UCD/Leinster/124)
12 – Luke Marshall (Ballymena/Ulster/2)
11 – Keith Earls (Young Munster/Munster/38)
10 – Paddy Jackson (Dungannon/Ulster/2)
9 – Conor Murray (Garryowen/Munster/18)
1 – Cian Healy (Clontarf/Leinster/38)
2 – Rory Best (Banbridge/Ulster/66)
3 – Mike Ross (Clontarf/Leinster/28)
4 – Mike McCarthy (Buccaneers/Connacht/9)
5 – Donnacha Ryan (Shannon/Munster/27)
6 – Peter O’Mahony (Cork Constitution/Munster/13)
7 – Sean O’Brien (UCD/Leinster/26)
8 – Jamie Heaslip (Dublin University/Leinster/56) Captain
Replacements:
16 – Sean Cronin (St. Mary’s College/Leinster/25)
17 – David Kilcoyne (UL Bohemians/Munster/6)
18 – Stephen Archer (Cork Constitution/Munster)*
19 – Devin Toner (Lansdowne/Leinster/4)
20 – Iain Henderson (Ballynahinch/Ulster/4)
21 – Paul Marshall (Belfast Harlequins/Ulster)*
22 – Ian Madigan (Blackrock College/Leinster/1)
23 – Luke Fitzgerald (Blackrock College /Leinster/25)
