At some point Kolkata Knight Riders may have to decide if they can afford to wait for Mitchell Starc to find form.

Starc has struggled again to justify his billing as Rajasthan Royals matched the highest run-chase in Indian Premier League annals, overhauling KKR's 6-223 on the final ball at Eden Gardens.

The most expensive player in IPL history at $4.43m now has five wickets for 232 runs in his six matches for KKR, and averages 10.54 per over.

After showing signs of being back to his best on Sunday when he took 3-29 against Lucknow Super Giants he was dispatched for 50 in four overs.

The numbers do not tell the full story. Yashasvi Jaiswal Starc without the ball going to hand in the opening over, Sanju Samson was then dropped off a sitter by Varun Chakravathy at short third. But it was nevertheless another chastening night for the 34-year-old.

England's white ball skipper Jos Buttler, so often the scourge of Australians, was his nemesis. Buttler made a stunning 107 not out off 60 balls, the last 60 in 30 balls as he masterminded a run chase in which he had to turn down singles to keep the strike.

Buttler hit 29 runs off the 15 legal balls Starc bowled at him, and the left-armer also conceded eight wides bowling at the centurion.

Royals' two-wicket win was harsh on Sunil Narine, the Trinidadian allrounder who made 109 with the bat then took 2-30 in four overs, the best economy-rate of another runfest. He won three of the many post-match awards and picked up them all without a smile.

The match pitted first against second, and after it Royals had opened up a four-point lead at the top of the standings. KKR are one of three teams chasing them on eight points, with little scope for failure.

The home side had looked on course for victory after Narine had scored a 49-ball century, dominating an innings in which no one else scored more than 30

But Royals began well, bringing up the 100 in the ninth over. Starc opened again, but his first ball was a wide and it did not get much better. Yashasvi Jaiswal hit him for two fours in the opening over, Buttler did the same in his next.

Narine slowed them down and Royals found themselves needing 96 off the last four overs. Buttler, 42 off 32 at that point, now moved into top gear, with Rovman Powell (26 off 13) adding acceleration.

Narine dismissed his fellow West Indian before Starc came back to bowl the 17th. He ran out Trent Boult but was hit for 12 and six wides, and could not prevent Buttler stealing the strike.

Nor could anyone else as Buttler, though struggling with exhaustion and a muscle injury, faced the last 18 balls, during which 47 were scored.

"Keep believing" was his mantra, said Buttler, when asked how he had turned the match upside down.

It is not a bad philosophy for Starc to follow. His class, he must hope, will eventually shine through.