Brentford slumped to their seventh defeat in nine games with a 3-2 home defeat at the hands of Swansea.
Ollie Watkins and Said Benrahma gave the hosts hope but squandered a string of clear-cut chances to pull off an unlikely comeback.
Swansea took just 25 seconds to break the deadlock, Barrie MacKay robbing hesitant Bees centre-back Ezri Konsa before squaring for Routledge to bundle home from close range.
They made it two midway through the half as Nathan Dyer cut the home defence to ribbons and his low cross eluded everyone but Brentford centre-back Mepham who could only watch as the ball bounced off him and into the gaping net.
And Swans made it three just before the half hour when Ollie McBurnie's audacious overhead kick dropped kindly for Fer who slotted home from eight yards.
Watkins reduced the arrears just after the interval, heading home from close range when Josh McEachran's 20-yard piledriver bounced back off the bar.
And Benrahma gave the Griffin Park faithful hope on 69 minutes with a delightful curling free-kick up and over the Swans wall that gave keeper Erwin Mulder no chance.
The only down side for the visitors was the loss of Martin Olsson, carried off with a suspected Achilles injury after an eight-minute delay with just four minutes gone.
Brentford had their chances in the first 45, Benrahma twice going close and seeing a long-range drive clip the top of the bar as Brentford tried to find a foothold in the game.
Matthew Grimes also went close for the Swans but his dipping 20-yard drive flew just over, before Neal Maupay's shot failed to lack the conviction to test Mulder.
The half-hour of chaos left a shaky Brentford looking shellshocked but they managed a reply just before the break that gave them momentum in the second half.
And Daniel Bentley was forced into a full-length save at the foot of his post after Joe Rodon found acres of space at the back post and should have scored with a powerful downward header.
Brentford looked brighter after the break but Bentley still had to be at his best early on to deny McBurnie, first from a header and then a shot from the edge of the area.
Brentford really should have got themselves back into it earlier but Maupay, in acres of space with just the keeper to beat, dithered and the chance was gone.
Skipper Romain Sawyers fizzed a 25-yard drive just past the upright and Alan Judge fired feebly wide as Brentford laid siege to the visitors' goal.
Benrahma's free-kick ensured a nail-biting finale for the visitors, but when substitute Sergi Canos' acrobatic volley from a Henrik Dalsgaard knock down flashed off the bar the game was up.