By Patrick Johnston
BRASILIA, July 4 (Reuters) - Tightening up a once leaky defence and marauding forward to support a goal-shy attack, the work of Belgium full back Jan Vertonghen is never done.
The 27-year-old, who began life as a central defender, also frequented the defensive midfield positions for a time but has been Belgium's flying full back in their run to the World Cup quarter-finals.
There he will face Lionel Messi's Argentina at the Brasilia national stadium on Saturday where his first priority will be to keep out the Barcelona magician.
Belgium coach Marc Wilmots was confident that his defender, part of a backline which has conceded only three goals in Brazil, could cope with the feared South Americans and get forward to support an attack that has managed six goals in four matches.
"When I took over two years ago I was told there was a problem with the backline," Wilmots, the former Belgium international, told reporters on Friday.
"We first make a compact block with five defenders, four plus (midfielder) Axel (Witsel).
"Now what I appreciate in this tournament is that my backs have made some breaks. I'm very happy with their evolution. They participate in the attacks and their defensive work so it works better and better for me.
"For this you need ... to find the balance between the defence and attack and for the moment the two full backs, one here next to me, do that," he said of Vertonghen.
The 27-year-old Tottenham Hotspur defender had paid the price for a sluggish start in the late 2-1 victory over Algeria in their Group H opener, being dropped for the next match against Russia.
His spell on the sidelines did not even last a half, though, as he was an early replacement for the injured Thomas Vermaelen and went on to skipper the side in their final Group H match against South Korea, even notching the 78th minute winner.
That goal made him Belgium's joint leading scorer in Brazil and he has been determined to add to his sole strike, appearing in the opposition penalty area almost as much as his own.
He flew up and down the left flank so much in the 2-1 extra time last-16 win over the United States that he vomited on the pitch.
But his bursts forward are likely to be restricted on Saturday with his first priority to shackle the formidable Messi. A task that would frighten many but not the confident Belgian.
"I think he has been outstanding so far, he is obviously their main man, but they have many other players to watch out for," Vertonghen told reporters, talking up the talents of Ezequiel Lavezzi, Sergio Aguero and Gonzalo Higuain.
"So we have to defend as a team like we did in the other games and we will be strong enough to stop him. I am convinced we can do that.
"We have been able to show we are quite confident in ourselves. We want to do this again and we feel very strong physically and mentally and I don't think we need fear anyone." (Editing by Ed Osmond)