(Reuters) - Barcelona fans enjoying Javier Mascherano's brilliant World Cup performances in midfield for Argentina have probably been asking themselves the same question - why doesn't he play there for us?

After he moved to La Liga from Liverpool in 2010, then-Barca coach Pep Guardiola converted Mascherano into a center back, where he has sometimes looked out of his depth and his lack of height is a severe handicap.

The player nicknamed "Jefecito" (Little Chief) still plays in his old midfield holding role for his country and his hugely impressive displays in Brazil are a big reason why Argentina are preparing to play in Sunday's final against Germany.

"It was Mascherano and 10 others," former Argentina captain Diego Maradona said after Wednesday's semi-final victory on penalties over the Netherlands.

Although his team mate Lionel Messi has been grabbing most of the headlines, the tireless Mascherano has been perhaps the best performer in his position at the World Cup and is a calm and reliable presence at the heart of the Argentine team.

He covers immense swathes of the pitch, rarely misplaces a pass, looks comfortable moving forward with the ball and is a ferocious tackler, likened to a "pitbull" by Maradona.

One moment that sums up his contribution came in Wednesday's semi-final against the Netherlands when he raced across and flung himself full length to block an Arjen Robben shot on goal.

It was all the more impressive as Mascherano was close to being substituted earlier in the match after a clash of heads with an opponent left him reeling.

The 30-year-old, who has 104 international caps and is the only Argentine to have won two Olympic soccer gold medals, has accumulated impressive statistics at the finals.

He has the best pass-completion rate (86.6 percent) and has made the most tackles (28) of any player.

Against the Dutch, he made more touches of the ball than any team mate (104) and has played all 600 minutes of Argentina's six matches in the tournament.

As well as his playing contribution, Mascherano is a heavyweight in the dressing room and clearly has the total respect of his team mates, including captain Messi, who also plays for Barca.

Moments before Wednesday's shootout, Mascherano was captured on camera telling goalkeeper Sergio Romero: "Today you are going to be a hero".

Romero was indeed the hero as he saved two Dutch spot-kicks and Mascherano shed tears of joy after Maxi Rodriguez scored the decisive penalty to send Argentina into the final.

"We hope to crown it on Sunday with the title, but beyond that I am just proud of this squad," Mascherano told reporters.

"It is a dream for all of us, giving Argentina this chance again," he added.

"We played a brilliant match, we didn't fear anything even though we knew that on Sunday we could be playing the match of our lives."