Slinfold’s superb 100 per cent record was ended by East Grinstead 2nd and as a result they slipped off the top of the table.
The hosts inflicted the Division 4 high flyers with their maiden defeat of the campaign with a six-wicket success in Division 4.
A unusually poor show with the bat saw Slinfold skittle for just 119 runs after they lost the toss on Saturday.
The opening four batsman managed just 13 runs between them and were at 13-3 when topscorer Mushal Murad joined the fray.
He battled to 23 and received some assistance from final three, Imran Shah (12), Dan Graycon (19) and Richard Harris (ten), after the early bowling of Sam Jackson (4-32) had done the damage.
In reply, openers Thomas Beswick (26) and Adam Stephenson (23) gave Grinstead a good platform, before both fell victim to Akeem Jordan (3-25).
And despite falling to 68-4, an unbeaten 45 from Ben Henderson saw them home with 122-4 in the 31st over.
Injured Slinfold captain Tom Filby said: “Unfortunately our batsman failed to adjust to a fast bouncy pitch and we were bowled out for our lowest total of the year. The top order was unable to see off the new ball which lead to our lower order scrapping for every run they could.
“Mushal Murad did his best to hang in for as long as possible and batted admirably to try and save the innings. Dan Graycon also batted well at the end to get us up to 119 and showed what was possible on a decent batting pitch.
“Fair play to East Grinstead their opening bowlers bowled well but we would have hoped to post more like 200. Our bowling is our strength and even though we knew we were under par we were confident that we could bowl Grinstead out. We needed early wickets and unfortunately they didn’t come.
“Richard Harris couldn’t repeat the magic of the week before and the East Grinstead openers played Akeem very well. Akeem did eventually make the breakthrough and at four down we had a sniff but we couldn’t take advantage and in the end East Grinstead chased it down comfortably.
“We have a massive game next week against Steyning and we will need to play much better to stand a chance.”