A contentious 76th-minute try to Bronson Xerri has given Cronulla an unconvincing 18-12 NRL victory over St George Illawarra at PointsBet Stadium.

Scores were level on Sunday when the Dragons inexplicably allowed a Shaun Johnson bomb to bounce into the hands of Xerri, who ran through untouched.

Replays later showed Wade Graham might have touched the ball in the lead-up, and the Sharks went on to win and move back into the top eight.

It was, however, a flimsy showing from John Morris’ side three weeks out from the finals, completing just 68 per cent of their 40 sets.

And they did it against a Dragons side whittled down to 14 fit players for almost the final 20 minutes due to three concussions.

Paul McGregor had also used up all eight of his interchanges with 15 minutes left, but his men showed plenty of courage in pushing for an upset.

In a sour note for Cronulla, star fullback Matt Moylan limped off with a suspected knee injury midway through the second half.

The Dragons were down by six points for most of the second half when, after repeated sets in attack, makeshift halfback Luciano Leilua spun over to level the contest.

Xerri had a chance to settle the match in the 71st minute, but was denied by a remarkable one-on-one tackle by Dragons rake Cameron McInnes.

But, in front of a crowd of 13,652, the rookie centre made up for the miss with his last-gasp effort, which pushed Penrith out of the top eight.

The signs were ominous for the Dragons from the moment Mikaele Ravalawa, who finished with five errors, dropped a Johnson kick in the third minute.

Costly errors early in the tackle count followed, and the Sharks made them pay with Aaron Woods and Sosaia Feki tries within three minutes.

A knockout blow went begging on the half-hour mark when Johnson fumbled a simple Xerri pass with the tryline in sight.

The Dragons reduced the lead to six at halftime after second-gamer Jackson Ford pounced on a Euan Aitken grubber that wrong-footed Moylan.