McGhee felt naivety contributed to the concession of both St Johnstone goals in a 2-1 defeat at McDiarmid Park, including Tam Scobbie’s last-minute winner.
It was the sixth time Motherwell have conceded a late goal in 2016 and they have now cost McGhee’s side six Ladbrokes Premiership points plus their place in the William Hill Scottish Cup.
Motherwell had edged a poor opening spell before Louis Moult headed in James McFadden’s 33rd-minute corner but Saints came alive immediately. David Wotherspoon was the catalyst, and the midfielder swerved a shot inside Connor Ripley’s near post two minutes before half-time.
It was a brilliant strike but a poor goal for Motherwell to concede as it came from a throw-in. Louis Laing had retreated to leave Saints with three against two out on the left and Chris Cadden went out to close down Liam Craig, who passed inside to Wotherspoon.
For the winner, McGhee felt Ripley gifted possession with an ill-conceived throw before teenager Ben Hall gave away an unnecessary free-kick with a tired tackle on John Sutton. But Motherwell’s deep defending from Simon Lappin’s free-kick was arguably more costly – they set up on the six-yard line, from where Scobbie met the delivery.
However, McGhee believes his young players and the team will benefit in the long run from the lessons.
McGhee said: “Even at the first goal, Cads [Chris Cadden] goes out to the thrower and the boy plays him inside. We’d ask that someone else should be out there as well but Cads made a bad decision.
“Now, what you get when you put young boys like Ben [Hall]and Cads and Connor [Ripley] in the team is they are here to learn. That’s why Middlesbrough sent Connor up here, to learn. Cads is in the team and we know he’s going to make mistakes, we know Ben is going to make mistakes, and you just hope you are not punished for it.
“But, as I said to them, the important thing for them is that they learn from it. They are on a learning curve and if they learn from that mistake and it doesn’t happen the next time then they will be a better player for it.
“That will be the cost of introducing young players to the team, as we are trying to do, and we have got to live with that.”
The McDiarmid Park pitch cut up badly, unsurprisingly given the ongoing wet weather, and the quality of football was poor as a consequence. But Saints manager Tommy Wright was unconcerned after his side finished the stronger team to end a nine-game run without victory and move up to fifth. “Particularly on the run we are on, it’s important to get the win,” he said. “And at this stage of the season it’s all about getting three points.
“The pitch is a lot better than what it has been but a lot of teams are basically playing percentage football. For whatever reason we didn’t pass it well enough in the first half and left Macca (Steven MacLean) too isolated. But we changed the shape and David got on the ball a lot more.”