Selsey had Jon Bines sent off as they drew 1-1 at home to Ringmer.
Warren Byerley gave the visitors a half-time lead and Bines had already departed for a second bookable offence when Alun Morey levelled 20 minutes from time.
Selsey boss Danny Hinshelwood said: "It seemed it needed the sending off to spark us."
Sidley United won 2-1 at home to Shoreham.
Graham Morris opened the scoring for Sidley from a free kick and Lee Wood added a second with a header. Darren Annis replied for Shoreham.
Sidley joint-boss Peter Heritage said: "We should have won at a canter. Kevin Rose could have had a hat-trick of headers."
A rare mistake by Hassocks' goalkeeper Pat Harding proved costly as his side went down 2-1 at home to Redhill.
Harding and Nick Newman got in a tangle over a back pass and Luke Jones nipped in to score after two minutes. Jon Difford (18) added a second before Mickey Turner pulled one back.
Robins' boss Dave John said: "Pat had a bad day but he's entitled to that because he's saved us on several occasions this season."
Sidlesham won 2-1 at Littlehampton to keep alive their hopes of a top six finish despite being without Richie Davies who was with Bognor.
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