Sydney Sixers may have lost Tom Curran for their BBL finals push but the English allrounder has agreed to make the harbour city his summer home for the next three seasons.

Curran signed a three-year contract extension with the Sixers before flying out to join England's squad for their one-day series in the Caribbean.

The 23-year-old has been a revelation in his first BBL season, taking 20 wickets and adding 185 runs with the bat in 14 games for the Sixers.

His Sixers teammate and countryman Joe Denly, who posted a maiden Test half-century for England on Tuesday (Australian time) against the West Indies in Saint Lucia, said Curran had even more to offer.

"No one works harder on their game than Tom," Denly said.

"I think he's only going to get better, which is great for the Sydney Sixers and great for England."

Unable to call on injured Test pacemen Mitchell Starc or Josh Hazlewood, the Sixers will sorely miss Curran for Friday night's away semi-final against the Melbourne Renegades.