The man who coined the term "Grexit" said the risks of a Greek exit from the euro zone have not gone away, despite the country having its credit rating upgraded on Tuesday.
"Now I think the risks are not that much changed from where they were a year ago. Those risks have clearly not gone away and they won't go away for a number of years," Ebrahim Rahbari, director of global economics at Citi Research, who coined the term in February 2012, told CNBC.
"Back in February 2012 the chances that Greece was going to leave [the euro zone] were still going up - in fact they weren't all that high when I coined the term and then they went up a few months later," he told CNBC Europe's "Squawk Box."
Rahbari's comments come as Greece appeared more optimistic about its future. On Tuesday, the government announced that it hoped to return to the international debt market in 2014 and Fitch ratings lifted its credit rating on Greece to 'B-' from 'CCC.'
(Read More: Greece Reclassified as an 'Emerging Market')
Though still a junk rating, the upgrade will give the country another glimmer of hope that its harsh austerity program is having an effect. The yield on Greece's 10-year benchmark bond fell below 9 percent for the first time since 2010 on Wednesday and in another sign of ebullience, Greek Prime Minister Antonis Samaras was headed to China on a trade mission on Wednesday.
Rahbari said a "large part" of optimism over Greece has to do with markets discounting the risks posed by the country.
"Whenever markets see an abundance of liquidity and the need to make returns and wherever there is a justification not to see an immediate meltdown I think optimism prevails, I don't think there's a large degree of reflectiveness about Greece in the medium-term."
(Read More: Greece, Cyprus May Be Forced to Exit Euro: Citi)
The International Monetary Fund (IMF), one of Greece's lenders, has also praised the progress in reducing government debt and improving its competitiveness, but it also said Athens needed to follow through on structural reforms to ensure its economy recovered. Greece's debt to GDP ratio in April was 156 percent - down from 170.3 percent in 2011, according to figures published by Eurostat in April.
Bob Parker, senior advisor at Credit Suisse, told CNBC said that another positive factor for Greece was the recapitalization of the country's banking sector.
"That problem in the Greek banking system is slowly easing away," Parker said, adding that the risk of Greece leaving the region was still "elevated."
(Read More: Top Hedge Funds Bet on Greek Banks)
In a dramatic turnaround, some of the world's top hedge funds are looking to make big investments in Greek banks, which are seeking investors for their recapitalization plans.
"The question is, in a year or two's time, will investors already have become complacent that risks have gone down again?" Rahbari asked. "The fact the people will be more exposed than they are now means that the risk of contagion will be larger."
-By CNBC's Holly Ellyatt, follow her on Twitter @HollyEllyatt