Headed goals in each half from Devante Cole and Peter Hartley had earlier put the home team in the driving seat as they consolidated their place in the top four.

The first 20 minutes were a non-event with St Johnstone sitting deep and being unable to capitalise when Motherwell conceded possession in their own half on several occasions.

Motherwell winger Jermaine Hylton began to look dangerous, setting up one of two half-chances which Christopher Long hit wide before coming close from 25 yards after a smart turn.

The wide man made the difference in the 29th minute when he turned his man near the bye-line and stood up a cross for Cole to nod home from close range to make it four goals in nine matches for the striker.

The visitors threatened when Chris Kane back-heeled David Wotherspoon's cutback towards goal but Mark Gillespie made a comfortable save.

Motherwell came close just before the break when Hartley's header was cleared off the line from Liam Polworth's corner.

They scored from the same source inside four minutes of the second half when the home skipper attacked the midfielder's delivery to power home a header.

Cole fluffed a good chance to put the game out of sight after bursting through the middle and the visitors came back into it.

Matty Kennedy carved out a great chance for himself to pull one back when he cut past Liam Grimshaw but the winger shot wide of the near post with only Gillespie to beat.

Ali McCann and Kane also failed to hit the target from decent opportunities before Tommy Wright made a double substitution midway through the half and changed to two up front with Michael O'Halloran joining Kane.

McCann soon drilled inches wide from long range and Zander Clark kept Saints in the game with a decent stop from Hylton's curling effort.

But the hosts soon moved out of sight after a 72nd-minute corner. Declan Gallagher's looping header bounced off the post and Carroll was on hand to force home the rebound.

Saints defender Wallace Duffy was forced off with a knee injury after going down under no pressure.

And there was further misery for the visitors when French striker Manzinga, whose debut was delayed by a hamstring injury, finished confidently after O'Hara headed on Scott's lofted pass.