Motherwell, who had Josh Law in for the injured Louis Laing, moved up to sixth while United remain eight points adrift.The visitors fielded their third goalkeeper in as many games, Michal Szromnik returning from illness to replace the absent Luis Zwick as Eiji Kawashima remained out with a thigh problem. They also had Callum Morris and Gavin Gunning back in defence.The bottom club showed real purpose going forward in the first half with John Rankin getting beyond the midfield and Paul Dixon causing problems on the left and both had shots inside 60 seconds but failed to test Connor Ripley.Motherwell should have scored in four minutes when Chris Cadden’s low cross found McDonald six yards out but Szromnik just stopped his effort going over the line. Marvin Johnson’s virtuoso display inspired Motherwell to a 2-1 victory as they came from behind to leave Dundee United deep in relegation trouble.Henri Anier finished brilliantly to put the Ladbrokes Premiership’s bottom club ahead in the 22nd minute but Johnson headed an equaliser in stoppage-time of a very open first half and set up Louis Moult to net a 65th-minute winner.United had cause for complaint against referee Crawford Allan, who missed Scott McDonald’s elbow on Coll Donaldson and punished Ryan Dow for a hard but ball-winning tackle on Motherwell substitute Morgaro Gomis to allow the hosts the free-kick that sparked their equaliser.But Motherwell also overcame adversity to secure a third consecutive win after losing central midfielders Stephen Pearson and Keith Lasley to injury. McDonald was soon flagged offside as he followed up Johnson’s saved shot after great skill from the Englishman.Another offside flag denied Anier as he netted at the third attempt following Dixon’s cross before Szromnik just held another Johnson strike.The breakthrough came when Rankin burst on to Billy McKay’s header and fed Anier. Steven Hammell appealed for offside but the Estonian had been level and capitalised on the hesitation by lashing a left-footed shot into the top corner from 20 yards for his third goal in two matches.Chances kept coming and Ripley pushed away Dixon’s long-range drive before Johnson brilliantly beat two men and fired just wide. McKay soon got in behind the home defence but Ripley parried his strike.There was no surprise about the Motherwell goalscorer when the equaliser came but the nature of the goal was, Johnson leaping to loop a backward header over the stranded Szromnik following Law’s delivery.Motherwell started the second half well and Johnson caused panic with a great turn and cross before his deflected chip hit the bar.The hosts lost skipper Lasley following an unforgiving 50-50 with Morris, but replacement Dom Thomas almost set up Johnston twice in a minute before the hosts took the lead.From his new position in midfield, McDonald fed Johnson who delivered a perfect low cross for Moult to tap into an empty net.Motherwell remained in control until the late stages when Ripley and his defence dealt with some aerial pressure before Johnson almost scored another in injury time.Copyright of Press Association 2016.