Despite leading 1-0 after the first leg, Dublin side couldn't find a way through CSKA defence.
St Patrick's Athletic are out of Europe.
They lost 2-0 on the night to CSKA Sofia in their Conference League tie at Tallaght Stadium, going out 2-1 on aggregate.
Saints midfielder Jamie Lennon says it was a frustrating evening:
Sligo were eliminated 5-2 over both legs by Viking of Norway.
On the domestic front, champions Shamrock Rovers go to Derry City in the League of Ireland Premier Division tonight.
Elsewhere, Bohemians host Dundalk,
It's Drogheda United versus Shelbourne,
And UCD take on Finn Harps.
All of the games kick off at 7.45.
In the First Division, Cork City take on Treaty United, it's Waterford versus Galway United, Wexford play Cobh Ramblers and Bray Wanderers meet Longford Town.
In the English Championship this evening, Watford play Burnley.
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