Saints scored three late tries as Rhinos imploded, having Zane Tetevano sent-off and Bodene Thompson and James Bentley sin-binned, all in separate incidents.
The trio had each played well and would have received higher marks, but for those lapses.
Harry Newman had a fine game in his second start of the season, but Leeds finished well beaten and a top-six place is now looking unlikely.
Here's how the Rhinos players rated, along with marks for the Saints side and referee.
. Zak Hardaker (squad number 33)
Some decent cover-tackling, but a couple of unfortunate moments 6 Photo: Ed Sykes/SWpix.com
. David Fusitu’a (No 2)
Continues to impress, set up the first try and ran strongly from the back 7 Photo: Phil Daly/Leeds Rhinos.
. Harry Newman (No 3)
Had a fantastic first half, scored a dazzling try 8 Photo: Ed Sykes/SWpix.com
. Rhyse Martin (No 12)
Found it tough defensively against an inspired Konrad Hurrell 6 Photo: Allan McKenzie/SWpix.com
. Ash Handley (No 5)
Very willing, did well for the second try but picked up an injury 6 Photo: Alex Whitehead/SWpix.com
. Blake Austin (No 6)
Some effective moments, particularly with the boot, but was playing behind a beaten pack 6 Photo: Ed Sykes/SWpix.com
1. Zak Hardaker (squad number 33)
Some decent cover-tackling, but a couple of unfortunate moments 6 Photo: Ed Sykes/SWpix.com
2. David Fusitu’a (No 2)
Continues to impress, set up the first try and ran strongly from the back 7 Photo: Phil Daly/Leeds Rhinos.
3. Harry Newman (No 3)
Had a fantastic first half, scored a dazzling try 8 Photo: Ed Sykes/SWpix.com
4. Rhyse Martin (No 12)
Found it tough defensively against an inspired Konrad Hurrell 6 Photo: Allan McKenzie/SWpix.com
5. Ash Handley (No 5)
Very willing, did well for the second try but picked up an injury 6 Photo: Alex Whitehead/SWpix.com
6. Blake Austin (No 6)
Some effective moments, particularly with the boot, but was playing behind a beaten pack 6 Photo: Ed Sykes/SWpix.com