The Motherwell captain announced his retirement earlier in the week but he could not end on a high as goals from Johnny Russell and Jon Daly secured a comfortable victory for United.
After a slow opening to the match, the visitors opened the scoring after eight minutes. Darren Randolph in the Motherwell goal did well to deny Stuart Armstrong on two occasions before Russell bundled the ball over the line from close range.
United came close to doubling their lead when Russell broke away from Tim Clancy on the left flank and his cut-back found John Rankin, who struck the outside of Randolph's post from a tight angle.
Paul Dixon clipped the top of Randolph's crossbar with an excellent free-kick five minutes before the interval before Michael Higdon came agonisingly close to levelling the game when he powered a header just wide of the target following a pinpoint delivery from Tom Hateley.
Randolph produced a wonderful piece of goalkeeping to keep out Daly's curling effort just before the hour mark. United doubled their advantage with nine minutes remaining, Russell set up Daly, who had the simple task of rolling the ball into the net.