Forlan failed to get on the scoresheet in Uruguay's goalless draw with France on Friday but he has earned a reputation as one of the world's leading marksmen over the last few years. Since leaving Manchester United for Spain in 2004, the 31-year-old has struck goals galore for Villarreal and Atletico Madrid - twice winning the European Golden Boot in the process.
Now the former Independiente forward will be looking to get his FIFA World Cup tally up and running by firing Uruguay to victory against the hosts this evening. The vastly experienced Parreira knows what to expect though, saying: "He's a player you can't leave free - you've got to keep eyes on him the whole time.
"I remember him from the Brazil national team and he always used to score against Brazil. He was one of the top scorers in the Spanish league. He's in top shape now, good form. We have to keep an eye on him for the whole 90 minutes."
South Africa captain Aaron Mokoena is also aware of the threat posed by the South Americans. "They are a very experienced side who defend very well," he said. "They have two fantastic forwards. We all know Forlan, who is full of confidence. We have done our homework on them. We've analysed their strong points. They are a very experienced side and we are looking forward to the game."
Bafana Bafana began their FIFA World Cup campaign with a 1-1 draw against Mexico in Soccer City. Parreira's troops struggled at the outset but then gained in confidence and came within 11 minutes of claiming the victory before being pegged back by Rafael Marquez's equaliser.
"I've never played a team like Mexico. They play unusual football, but we have to focus on next game," he said. "We've forgotten about Mexico. We wanted to win but it's good not to lose the first game and now we move onto the Uruguay match, which is absolutely vital for us."
He added: "We would like the fans to get behind us more. They've been behind us but it would be great to have that support. It's a game where we really need them behind us."
Uruguay coach Oscar Tabarez and captain Diego Lugano are expecting a memorable experience at Loftus Versfeld Stadium. Tabarez said: "Playing against the World Cup hosts is always very special, with the atmosphere and all those expectations."
Lugano added: "I think it's going to be great match with a great atmosphere. We are going to give our very best and try to make Uruguay happy."
Regarding his side's draw with France, the Fenerbahce defender added: "I think we ended the match with a feeling that we could have had a better result with more accuracy in front of goal. We know (today) is going to be very different - perhaps we need to be more aggressive in attack to assure ourselves of the three points."