The nine-time champion has won the last seven straight Argentina events, but his part-time schedule means he has not competed since finishing second to championship leader Sebastien Ogier in Rally Sweden in February.
While he has stayed busy - notably making a winning start to his FIA GT Series career at Nogaro - Loeb fears his lack of WRC running, particularly on gravel, could harm his chances this weekend.
"Apart from one day of testing, I haven't driven on gravel since the 2012 Rally de Espana," Loeb said, "so I don't know what sort of feeling I'll have on the first few stages in Argentina.
"I think that you can lose your rhythm pretty quickly, and that's why I'm cautious about my chances.
"There's no denying the fact that I have pretty much moved on from rallying and am now focused on the future.
"This reduced programme is a good way to continue to compete for Citroen in 2013, but I'm not as well prepared as Mikko [Hirvonen], Dani [Sordo] and the other guys. We'll see what happens when we get our helmets on..."
Loeb admitted he had been impressed with VW during his absence - as Ogier triumphed in both Mexico and Portugal - but insisted Citroen's drivers are still in the title hunt.
"Obviously, I watched the rallies and saw how they went," he said.
"It wasn't always easy for Citroen faced with a rival that was already managing to combine very high levels of performance and reliability on a state-of-the-art car.
"But the season isn't over yet, because winning a 13-round championship where all the rounds count also requires consistency.
"We saw that the DS3 WRCs were quicker in Portugal than in Mexico, so that suggests that the team is making progress."
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- Sebastien Ogier