The Carnegie Challenge Cup holders were too good in sweltering conditions as circumstances conspired against Leeds.

Rhinos began the game without Brent Webb (back) and Ryan Bailey (ankle), who were joined on the sidelines by hamstring victim Jamie Jones-Buchanan.

Leeds' problems worsened when star scrum-half Rob Burrow was flattened trying to tackle Lee Gilmour and had to leave the action after just 17 minutes, though he returned mid-way through the second-half.

Later in the opening half they lost centre Clinton Toopi, who was carried off with what looked to be a serious knee injury, Saints scoring their second try with Leeds down to 12 men before they could get a replacement on.

On top of that, winger Ryan Hall and Danny McGuire were both hampered by leg injuries sustained in the early exchanges.

Leeds were also on the wrong end of some debatable decisions by the match officials, though in the end Saints were worthy winners, despite a spirited second-half fightback by Rhinos.

Saints led 18-2 soon after half-time, but Leeds cut the gap to six points and made a real fight of it in the third quarter.

Saints drew first blood on seven minutes, seconds after an escape at the other end.

Burrow crossed from Scott Donald's pass, but the touch judge raised his flag for a foot on the sideline before the winger got the ball away.

Gareth Ellis was penalised for a high shot on eventual man of the match James Graham following the scrum and in the subsequent set Sean Long dummied past Ellis, drew full-back Lee Smith and put Chris Flannery over, Long converting.

Desperate defence pulled Paul Wellens down just short moments later, then Hall made an heroic catch to deny the on-rushing Leon Pryce from the stand-off's own kick.

Rhinos had another let-off on 22 minutes when Keiron Cunningham and Long created an opening for Pryce, but he spilled the ball in Smith and McGuire's joint tackle as he tried to stretch over.

Leeds had little ball and almost no territory in the opening 28 minutes, but got points on the board through a Sinfield penalty after Wilkin fouled Smith.

Rhinos did well to restrict Saints to just one try as late as the 36th minute, but back-to-back penalties carried the holders up field for Long to send Pryce over for another converted try to make it 12-2 at the break.

That score came as Leeds defended with 12 men, following Toopi's injury.

Rhinos did have a chance to cut the gap after the hooter had sounded, but Sinfield couldn't find the target with a penalty attempt from right on half way.

Saints looked to have put the game to bed nine minutes into the second-half when Jon Wilkin scored their third converted try.

A knock-on by Simon Worrall turned possession over and Saints counter-attacked in devastating fashion as Gilmour worked a one-two with Francis Meli, whose pass was finished by Wilkin.

Saints had missed a chance two minutes earlier after they ran a kickable penalty near the Leeds line. Long, Pryce, Wellens and Matt Gidley worked the ball to Gardner, who looked a certain scorer, but lost possession in Donald's muck-or-nettles tackle by the flag.

Saints showed their quality on defence soon after the try as Leeds desperately tried to find a way back.

Jamie Peacock snatched possession, then Smith went close. On the next play McGuire and Senior linked to get the ball to Donald, but he was barged into touch a metre out by Gardner and Wellens.

Rhinos gave themselves a glimmer on 54 minutes when Ali Lauitiiti nipped over from acting-half and Sinfield converted, following a Jason Cayless knock-on.

And remarkably they were back in the game five minutes later, when Donald crossed at the corner from Senior's pass after a scrum following a Saints knock-on from McGuire's high kick.

Sinfield couldn't convert, but Burrow returned and Leeds suddenly had a sniff of something, but that evaporated as referee Ashley Klein and his assistants became the centre of attention.

First, Smith was penalised in possession. Then the officials allowed play to continue after Meli offloaded over the touchline and Klein ruled Smith had been trapped in goal, though he seemed to have got out.

From the drop out, Smith tackled James Roby too high – no arguments about that decision - and Long kicked the goal to nudge Saints two scores clear.

With 10 to go it really was game over as Lauitiiti knocked on and in the resulting set Bryn Hargreaves went over for Saints' fourth converted try, following good work by Long, Cunningham and Graham.

Leeds gained some deserved consolation in the final moments when Kylie Leuluai touched down from Burrow's pass, though Sinfield missed the straight-forward conversion attempt.