Brendan Rodgers has stressed the importance of Celtic keeping concentration at all times in tonight's clash with Zenit St Petersburg - and appears to have used Dedrcyk Boyata as an example.
Zenit visit Parkhead in tonight's first-leg Europa League encounter and the injury-hit Hoops are big underdogs to progress into the last 16.
Rodgers has some pretty big names missing through injury and the Northern Irishman is fully aware that his troops will need to be razor sharp in order to get anything from the game.
The Celtic boss has recalled a moment in the home defeat by Bayern Munich in the first half of the season, when Boyata missed the run of Kingsley Coman who went on to score.
And the former Liverpool manager is adamant that his boys can't afford similar lapses of concentration against the Russians.
He told The Telegraph: "Domestically, you can maybe assess the position and come away. At this level you have got to keep checking your space because the minute you come away from it and you don’t check they are gone.
“We saw a goal against Bayern Munich like that. Our centre half checks the winger, thinks he is in good position, doesn’t check again for a few seconds and when he looks back he’s gone. Coman is in and scores."
Boyata won't play any part in tonight's game through injury, meaning that Kristoffer Ajer and Jozo Simunovic are likely to continue in central defence.
Simunovic, like Boyata, has gone off the boil in recent weeks and months, so Rodgers needs a big performance from the former Dinamo Zagreb stalwart tonight - and one without mistakes.