The Trotters fell well below their recent standards as they slumped to a 3-0 home defeat to Clint Dempsey-inspired Fulham, though favourable results elsewhere ensured they remained outside the bottom three.
Coyle had been expecting much better after entering the game on the back of a three-match winning run, and said: "It is disappointing because of how we came into the game, and being at home, looking to make it four wins on the bounce."
And with other results going their way, he added: "We had a chance to open up a bit of a gap, so all in all, it is disappointing."
Bolton paid the price for a lacklustre first half as Dempsey took his goal tally for the season to 21 by following a stunning 30th minute free-kick with a firm header on the stroke of half-time.
He narrowly failed to score a third hat-trick of the season as he shot into the side-netting when well placed in the second half but Mahamadou Diarra wrapped up a convincing win late on.
Fulham manager Martin Jol hailed the American's performance, although he felt he should have had another treble. He said: "It would probably have been his first hat-trick away from home - but he will always be on the end of things, like he was for the second goal."
After taking a grip of the game, Fulham rarely looked troubled even as Bolton applied pressure in the second half.
Jol said: "I think we defended well and kept the ball well, then you will create chances. That is the main thing. If you play good football then you will score goals."
The only downside for Fulham was a second half foot injury to Costa Rican forward Bryan Ruiz that could rule him out for the rest of the season. Jol said: "It is worrying - he has probably broken his metatarsal. That is a problem."