Goals from Tammy Abraham and Jordan Ayew either side of half time punctuated a thoroughly professional performance.
De Boer has endured a hard start to life as manager of Crystal Palace following two consecutive defeats and now ex-Eagles' boss Sam Allardyce has gone on to advise the Dutchman to focus on keeping things tight at the back before looking to play attractive football.
Chris Hughton's men have suffered back-to-back 2-0 defeats in the Premier League, and while there's absolutely nothing wrong on paper with two-goal reversals to Manchester City and away to Leicester, the worrying aspect is that they really didn't lay a glove on either side.
But both sides were still searching for their first goal of this league campaign and it was already being billed in some quarters as a relegation battle.
Swansea nearly went ahead before the break when Timothy Fosu-Mensah hesitated on the ball but Wayne Hennessey saved well from Abraham.
Stu Forster GettyImages
Swansea have looked shot-shy in their opening two games following the £45million sale of Gylfi Sigurdsson to Everton and the loss of last season's top scorer Fernando Llorente to injury.
At the start of the second half Palace had a great chance but Kelly's header was straight at Lukas Fabianski.
De Boer confirmed: "Ruben has a groin injury and is out for this week". The Swans also have an excellent defensive record at Crystal Palace, conceding just twice in 4 games.
Last season, Swansea defeated Crystal Palace 5-4 at Liberty Stadium and 2-1 at Selhurst Park.
"And that wasn't because Swansea did a fantastic job - this was a game in which two teams did not play their best and the team that makes less mistakes wins this type of game, which is what happened".
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