The transfer mill is churning once again, with Celtic believed to be lining up a move for Sam Johnstone, the goalkeeper from Wolverhampton. Sources close to the club suggest they are exploring options to reinforce their squad ahead of the run-in. Celtic have laid out their intentions, but valuation and timing remain under debate. Manchester United and Tottenham are keeping tabs in case talks collapse or progress slows further. Celtic's back line has been a real strength this season, conceding just 0.5 goals per game (1 in 2). Sam Johnstone would be expected to slot into that unit and hold his own in an already solid setup. Wolverhampton have also been linked with Joao Virginia while Celtic are reportedly monitoring Balazs Toth, Gvidas Gineitis and Landon Emenalo. Can't get enough Celtic transfer rumours? Follow @PlayerSwitchCom on Twitter for the latest transfer news as it happens.