Hughes captured Sidwell from under the noses of Premier League rivals after the Aston Villa man snubbed Wolves and turned down a move to West Ham.
The 28-year-old midfielder joins the Barclays Premier League club for an undisclosed fee on an initial six-month deal, which could potentially see him stay until the summer of 2014.
Hughes also revealed 33-year-old Murphy has been offered a new one-year contract and insisted there was no way Damien Duff, linked with a possible move to former club Blackburn, would be allowed to leave the club in the January transfer window.
But it is the capture of Sidwell, 28, who has played only four matches for Villa this season, which appears to have set Hughes' bid for January reinforcements in motion.