A fine 44 by Derbyshire-born batsman Tom Wood, on his List A debut for the county, helped Derbyshire to 281-7 their 43 overs, after rain delayed the start to the match.
But Sri Lanka A made light work of their target, with openers Niroshan Dickwella (67) and Dhananjaya de Silva (119) giving the tourists a flying start on their way to a seven-wicket victory with 10.4 overs to spare.
Slater and Wes Durston made a good start of their own, adding 67 for the first wicket before the skipper was first man out for 32.
Dilanka Sandakan put a brake on the Falcons’ early progress, taking the first of his five wickets with his left-arm chinaman bowling when Alex Hughes was dismissed for 15.
That brought in Charlie MacDonell for his first-team Derbyshire debut. MacDonell impressed with a century for Durham MCCU against Derbyshire at the 3aaa County Ground in April and played for the seconds earlier this month and the 21-year-old moved on to 19 before he became Sandakan’s second victim at 141-3.
Wood played some impressive shots on his way to 44, which included six fours and took only 41 balls as part of an 87-run stand with Slater for the fourth wicket.
The 22-year-old also fell to Sandakan but not before Slater reached three figures. It was his second century in only two completed one-day fixtures for Derbyshire and came off 105 balls with 12 fours.
But Matt Critchley (1) and Slater both fell within 11 balls as Sandakan took his final wickets for figures of
5-40. Greg Cork followed for eight in the push for late runs and it was left to Rob Hemmings to provide them.
Hemmings struck the last four balls of the innings to the boundary to finish 25 not out from 13 balls to help boost the score to 281-7.
That appeared a good 43-over total but the Sri Lankan openers soon took a big chunk out of it.
De Silva and Dickwella raced to a century opening partnership in only 10 overs and the pair carried their stand on to 161 when, off the last ball of the 17th over, Dickwella was stumped by Harvey Hosein off the bowling of Durston (1-37).
The left-hander faced only 47 balls and his 10 fours and a six for his 67.
Undaunted, de Silva pushed on and completed his century off 70 balls but was out for 119 when he attempted a ramp shot to Ben Cotton (1-50) and was caught at fine leg.
That was 212-2 in the 25th over and victory was just about in the bag for Sri Lanka A.
They lost one more wicket before the winning run came off the second ball of the 33rd over, Greg Cork taking an lbw decision against Mahela Udawatte for 22.
Bhanuka Rajapaksa (48 not out) and Ashan Priyanjan (nine not out) took their side to the win. (Courtesy derbytelegraph.co.uk)