Joint manager Gary Elphick said it was a frustrating night as Worthing Football Club lost 1-0 away to AFC Sudbury on Tuesday.
The hosts got the only goal of the game through Adam Tann on 30 minutes but Worthing had opportunities to draw level in the second half.
Corey Heath turned home Lloyd Dawes’ goalbound shot from a offside position and Worthing were unable to make the most of other dangerous openings.
On-loan Brighton striker David Ajiboye was unavailable for the game and Joe Taylor, who has joined from Leatherhead, made his debut in goal with Jack Fagan ruled out for up to six weeks with a hand injury.
Worthing dropped a place to ninth in the table with the defeat and are now six points behind Leiston, who occupy the final play-off place.
Worthing did not get back from the long away trip until 2am on Wednesday and Elphick said: “It was really frustrating and a bit of a sickener, to be honest.
“In the first half, they were probably the stronger side but we were playing uphill and didn’t think going in at 1-0 down was a bad scoreline.
“We were quite confident we could get back into it in the second half but were unable to take some glorious chances and we probably missed David up front.
“It’s a game we need to win if we’re going to be challenging for the league or the play-offs next season.
“There’s still a lot of games left this season but this result makes it a bit more of an uphill struggle to get into the play-offs.”
Worthing now have back-to-back home games, with Enfield the visitors to Woodside Road on Saturday and Harrow Borough on Tuesday.
Elphick said: “I think they are both must-win now and we’ve got to get six points.
“If we want to get into the play-offs, we’ve got to apply as much pressure as we can on the teams above us.
“Tonbridge are on a good run and we need the teams above us to slip up a little bit and a lot also depends on Leiston, who have a lot of games in hand.”
Defender Jack Cook could be back in Worthing’s squad on Saturday, while defender Will Hendon is still a couple of weeks away from returning.
WORTHING: Taylor; Boiling, Elphick, Heath, Rents; Hopkinson, Wills, O’Neill, Sparks; Dawes, Clark. Subs: Edwards (Hopkinson 67), Belward, Brodie, Williamson.
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