The Scotland wing has been outstanding for Glasgow this season despite opposing teams knowing he's a man to watch after his impressive first year at Hughenden.
It will be only the second league or cup match that Sean has missed since his Celtic debut as a replacement in the opening-day victory against Cardiff at Hughenden in September last year.
Injury kept him out of the home game against Connacht two weeks later, but he has started in all 32 games Glasgow have played since then – in the Celtic League and Cup and the Parker Pen Challenge Cup.
Sean is replaced on the left wing by his fellow cap, Andy Craig in the only change in the team who started the league match against Munster at Hughenden last week.
Despite the enforced change in the team, Hugh Campbell, Glasgows head coach, was upbeat today in thinking ahead to tomorrow's match. "After the frustration of last week we're looking forward to an outstanding performance against Ulster," he remarked.
Two changes have been made among the Glasgow replacements. David Millard has been recalled with Craig's promotion, and Euan Murray returns as back-up prop instead of Andrew Kelly.
Glasgow:
15 Rory Kerr
14 Kenny Logan
13 Graeme Morrison
12 Andrew Henderson
11 Andy Craig
10 Dan Parks
9 Sam Pinder
1 Kevin Tkachuk
2 Gordon Bulloch
3 Lee Harrison
4 Andy Hall
5 Dan Turner
6 Cammy Mather
8 Jon Petrie (captain)
7 Donnie Macfadyen
Replacements:
16 Scott Lawson
17 Euan Murray
18 Andrew Wilson
19 John Beattie
20 Graeme Beveridge
21 Calvin Howarth
22 David Millard