The Albiceleste topped the South American qualifying group with 32 points from 16 games and head into the match against Bosnia on the back of Friday night's goalless draw with Ecuador.
Coach Alejandro Sabella is reportedly ready to make a number of changes to his Argentina team with most of his stars - including Manchester City duo Sergio Aguero and Pablo Zabaleta, and Inter Milan forward Rodrigo Palacio - coming into the starting line-up.
Mascherano feels the team has improved over recent warm-up games and is hopeful Argentina will arrive at the World Cup in good form.
The Barcelona player said: "We must keep progressing and improving, but our intention is to play like we did in the second half against Ecuador, rather than how we played in the first half."
Angel di Maria, meanwhile, told TyC Sports channel and La Nacion newspaper that the team should know how to play without Lionel Messi, who has been ruled out through injury.
"We are in good shape even though Leo is injured, but it is better that these problems occur now and not closer to the World Cup," said the Real Madrid winger.
"I hope he can get over it as soon as possible. We have already played games without Leo and the national team coped well. These games are useful to firm up the team.
"We'll try to approach this game in the best way so we can pick up a victory in the last game of the year."
Bosnia, meanwhile, won European qualifying Group G with 25 points, beating Greece to automatic qualification on goal difference, and will feature at the World Cup finals for the first time.
Captain Emir Spahic is anxiously looking forward to playing the two-time World Cup winners at Busch Stadium - the home of baseball giants the St Louis Cardinals.
He told Bosnia's official website: "We are sure we can play this game at a high level and achieve a good result.
"Of course, we came here to do our best, we have to confirm that our qualification for the World Cup was not an accident and that we are among the best of the European teams."
Messi's absence is something the team are aware of but they also know that Argentina have other stars, such as Gonzalo Higuain and Aguero.
However, Zoran Krvzic does not fear the South American side's quality, saying: "We respect every opponent, but no one is afraid.
"I am only sorry that Messi will not play because it would have given us even more motivation to play well."
Full-back Avdija Vrsajevic added: "It will certainly be a tough match against one of the best teams in the world, but I am also convinced that we will give our best on the pitch and I believe that we can compete and get a good result."