Market positioning data released on Friday showed that net short positions in the euro/dollar – essentially a bet on the euro falling – have risen to their highest level since late May 2013.
"What is happening is that the euro is winning as the preferred funding currency and if that's the case there's nothing wrong with the market being short if it can get even shorter and there's plenty of money to be invested around the world," said Jesper Bargmann, head of trading, markets, Singapore at Nordea.
"I think there has been a true sentiment change towards the euro, which I do expect to go lower over the medium term," he added.
Europe's single currency has declined just over 3 percent from a 2-1/2 year high hit in early June, undermined by the ECB's decision to impose a negative interest rate on banks for their deposits and cut its main lending rate in a bid to lift inflation and a weak economy.
"The last time net positioning was at this level, euro/dollar was trading closer towards 1.30. For now, euro/dollar is supported above 1.35 and it would require a further increase in short bets to break below that level," analysts at ANZ Bank said in a note on Monday.
Currency analysts say the ECB's monetary easing has fueled the use of the euro for carry trades – borrowing money in a currency that is backed by low interest rates to fund investments in higher-yielding assets.
This means the tide is turning against the once-resilient euro.