St George Illawarra five-eighth Gareth Widdop inspired his side to a crucial 19-12 win over Penrith but the Dragons' finals hopes may yet take a hit after three players were placed on report in an ugly encounter at WIN Stadium on Thursday night.

Dragons second-rower Tyson Frizell (tripping), centre Euan Aitken (knees) and forward Jake Marketo (dangerous throw) will face anxious waits to learn on Friday whether they have been charged by the NRL match review committee.

Of particular concern for coach Paul McGregor will be the fate of Frizell, who has loading and carryover points from a recent high tackle on Canterbury prop Tim Browne, as fellow second-rower Joel Thompson was a late withdrawal from Thursday night's match after injuring his hamstring at training.

The Dragons face Gold Coast and Wests Tigers in their remaining two matches but they could fall out of the top eight if Canterbury defeat South Sydney on Friday night and Manly beat Parramatta by more than 24 points on Sunday.

It could have been far worse as St George Illawarra struggled to get on top of the hapless Panthers in an error ridden match that hung in the balance until the 75th minute when  Widdop converted his own try.

A 69th minute Benji Marshall field goal had regained the lead for the Dragons after they had earlier looked certain to win when Widdop kicked a penalty goal and put centre Peter Mata'utia over for try in the 15th minute.

Mistakes and penalties proved costly and it took two repeat sets late in the second half after defenders had chased long kicks from Widdop and Marshall to right the ship.

Marshall's field goal came on the set after Penrith fullback Will Smith had been driven in goal when he fielded Widdop's kick and the St George Illawarra defenders gave Josh Mansour the same treatment on the next set.

Marshall, who missed last week's loss to Brisbane with a hamstring injury, did not finish the match but is expected to be available next week.

There were three key moments midway through the first half that dramatically swung momentum Penrith's way after St George Illawarra had appeared headed for a comfortable win.

Firstly, Frizell was placed on report for an awkward trip on Smith as he chased a Jamie Soward kick in the 26th minute.

From the ensuing penalty, Aitken was also placed on report after his knees struck Tyrone Peachey in the head as he joined a tackle by Frizell near the tryline.

Until then, Penrith had only completed one set of tackles but the sudden shift in possession and field position saw winger David Simmons comfortably catch a cross field kick from Soward to score in the 27th minute.

An uncharacteristic error from NSW Origin fullback Josh Dugan after fielding a deep kick from Soward on his own tryline and flinging the ball into the ing oal before heading over the touchline piled the pressure on the Dragons.

Soward's kicking game caused further havoc for St George Illawarra and Bryce Cartwright was held up in the 31st minute after winger Justin Hunt was unable to take another crossfield kick but it was only a matter of time before the Panthers scored and they did so in spectacular fashion in the 33rd minute when Mansour crossed off a spectacular Lewis Brown flick pass.

Penrith lost captain Elijah Taylor early in the match with a broken hand.