The Drumcondra outfit will also used the fixture as match practice ahead of this day week's UEFA Cup qualifying round second leg home tie with Slovenia's Olimpija Ljubljana.
Fenlon awaits a fitness report on midfielder Wes Hoolahan who starred and scored in the Irish U21s 5-1 friendly win over Poland in Gdansk on Tuesday. Stuart Byrne is also out following a head injury picked up against Ljubljana last week.
'Wes has had a lot of travel between Slovenia and Poland in the last fortnight. I will weigh up all the options before naming my starting line-up. If necessary, striker Stephen Geoghegan will come into the reckoning,' said Fenlon.
'I thought we had enough chances to win the first match which ended in a scoreless draw at the Showgrounds on Sunday. There was obviously a bit of fatigue among the players, but we are just glad to still be in the competition and can take nothing for granted. The possibility of a quarter-final at home to Galway United is a real incentive for the players.'
Sligo must do without striker David O'Dowd, midfielder Gerry Carr and central defender Jim Sheridan for the visit to Dublin. All three are suspended but Ian Rossiter returns from a ban to bolster ranks.
ATOGB Predicition: Shelbourne 2 Sligo Rovers 0 (Match updates on the site from 7.30pm)
Elsewhere, Kilkenny City take on Dundalk in the First Division with the chance of moving off the bottom of the table and ahead of basement rivals Athlone Town if a draw or win can be garnered tonight.