They were wrong. The disparity was substantial. The difference was Michael Higdon and it does not come any bigger this side of an NFL offensive line.
The 29-year-old, from Liverpool, bullied the St Johnstone defence with his height and bulk and then applied three technically adept finishes to the chances he was offered.
The hat-trick provider has now moved on to 16 goals in 28 matches this season, with 15 of them in the Clydesdale Bank Premier League. He was wry about his movement in catching up with Chris Humphrey for his first goal but serious about his target for the season.
"This is my best season ever for goals per game," he said. "I got 16 last season so obviously I am going to beat that this year. I need to set my sights on being top goalscorer in the league with the chances I am getting. I have that ambition."
A consistently entertaining match was thus marked conclusively by Higdon's hat-trick but sprinkled throughout with opportunities scorned by St Johnstone. The Perth team seemed to have reached a collective pact to refuse to score past Darren Randolph, no matter the provocation. When the Irish goalkeeper came off after 76 minutes because of a hamstring strain, they almost immediately put two goals past Lee Hollis.
St Johnstone's early fecklessness, though, rendered these finishes defiant rather than point-winning. They set up a frantic finish to a match that had seemed over after 20 minutes when Motherwell sprinted two goals clear.
The opener came after nine minutes. Higdon swivelled on the halfway line to free the pacy Humphrey and the big striker then raised enough of a gallop to appear in the area to drive the winger's cutback past Alan Mannus.
His second followed 11 minutes later when the pace and drive was supplied by Henrik Ojamaa, who threaded a pass to Higdon who turned Frazer Wright and shot home, after his first effort ricocheted off Calum Davidson.
His third, on 69 minutes, was an unnecessary reminder to St Johnstone of his potency when he fired past Mannus after Shaun Hutchinson's header from a Tom Hateley corner had been cleared off the line and into his wide path.
This peerless finishing surely strained the forbearance of the 165 fans from Perth in the attendance of 3649 who watched their side enjoy significant possession, regular territorial advantage and create several chances through an enterprising front three of Peter Pawlett, Steven MacLean and Rowan Vine.
Despite infrequently frantic action around his goal, Randolph did not have a save to make before he limped off. He watched in some apprehension as Keith Lasley knocked the ball off the line after Hutchinson inadvertently headed a St Johnstone corner towards his own goal, and he could do nothing when Vine's deflected cross looped on to the bar in the second half.
With Motherwell 3-0 up, Hollis could have been forgiven for believing he was replacing Randolph for a gentle 15-minute workout. Instead, his two introductory touches involved picking the ball out of the net. First, substitute Nigel Hasselbaink shot beautifully past the keeper from the edge of the box and minutes later Liam Craig, who had been unfortunate with a series of shots, suddenly found his range and direction, and drilled a left-foot drive past Hollis.
The substitute goalkeeper, though, made a significant intervention when Hasselbaink wriggled through in the dying moments but Hollis smothered. Steve Lomas, the St Johnstone manager, later claimed his forward had been held back in the move and there seemed justifiable claims for a penalty, but it was symptomatic of the visitors' day that the foray ended in failure. There was further pain for St Johnstone as Lomas indicated Gary Miller may have broken an ankle.
In contrast, it was a day when Motherwell could be more than satisfied. A "relieved" Stuart McCall, the Fir Park manager, now sees his side just behind Inverness Caledonian Thistle on goal difference in the race for the second place, and hopes to retain his players as the transfer window offers only threats rather than opportunities.
"I would be disappointed and surprised to lose anyone," he said, then added of Higdon: "It is crucial big Michael stays to the end of the season if not longer."
Higdon, now four goals behind the £8m-rated Gary Hooper of Celtic, conceded it is also helpful to be scoring goals as his contract runs down, but added: "That takes care of itself. You end up where you end up. I just enjoy the moment."
This piece of Liverpool philosophy was complemented by a precise observation from Lomas who pondered Higdon's "conversion rate" . The manager knows this constitutes the most valuable of currencies. It was the difference last night.