The former Standard Liege man was eager to leave the Portuguese champions due to a lack of first-team football as he attempts force his way into Belgium's FIFA World Cup squad.
Defour's agent, Paul Stefani, duly revealed that the 25-year-old was on the verge of joining Premier League strugglers Fulham.
However, Porto then allowed midfielder Lucho Gonzalez to join Qatari club Al Rayyan SC, and the Argentinian's departure has opened the door for Defour to establish himself in Paulo Fonseca's side.
Stefani said: "Now Lucho's gone, Steven has to grab his chance as Lucho was the one blocking him.
"Steven was keen on joining Fulham. A few days ago, he even called Rene Meulensteen to discuss a transfer.
"He really wanted to move to Craven Cottage, where he could have signed for three-and-a-half years."
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