The defender was continuing in place of Gordon Greer after replacing the injured centre-back against Ross County in midweek, and he squeezed the ball over the line after Motherwell goalkeeper Russell Griffiths failed to deal with Chris Burke’s corner with any real conviction.
Jamie MacDonald was the busier of the goalkeepers and he played his part in sealing Kilmarnock’s 1-0 victory.
With Trevor Carson still out with a shoulder injury, Motherwell signed Gennadios Xenodochov on a short-term deal and put the Greek goalkeeper on the bench after going without back-up to Grififths for two games.
Motherwell arrived at Rugby Park on the back of a far higher-profile transfer, Louis Moult’s imminent switch to Preston, and Elliott Frear joined the injured striker plus Chris Cadden and Peter Hartley on the sidelines. Steven Hammell came in to a back four.
The visitors made a bright start and MacDonald made a good stop from Craig Tanner after he stabbed Gael Bigirimana’s first-time cross towards goal.
Killie settled and their best first-half move came when Youssouf Mulumbu took out three players with some good skill and fed Chris Burke, whose cross was headed over by Eamonn Brophy.
Motherwell had a better opportunity when Ryan Bowman’s backheel got Richard Tait in behind, but Alex Fisher shot too close to MacDonald from the cutback.
The hosts were ahead in the 42nd minute following Burke’s inswinging corner. Griffiths palmed it out under pressure but only as far as Boyd inside the six-yard box, and the defender forced it over the line off a Motherwell player.
Motherwell had to make a change immediately after the restart when Liam Grimshaw went off with a facial injury. Substitute Andy Rose soon had a header saved after MacDonald had got down well to stop Tanner’s drive.
Kris Boyd almost converted Burke’s low cross but most of the action was in the other box and Fisher headed wide after a corner, before being replaced by George Newell.
A diving Griffiths did well to stop a shot from substitute Jordan Jones with his feet after a deflection threatened to leave him stranded.
Motherwell continued to press for an equaliser. Bigirimana’s inviting ball just evaded a team-mate, Newell shot inches wide with an angled drive and another substitute, Ross MacLean, headed wide.
But Kilmarnock held on for a second successive home win and Greg Kiltie drew a decent stop from Griffiths in stoppage-time after making his comeback from a broken ankle off the bench.