Jackson Hastings starred for Newcastle in the pre-season match in Gosford on Saturday, chipping ahead for a Dylan Lucas try and setting up two others against an understrength Sharks outfit.
English recruit Will Pryce also scored a try in his first trial match for the Knights, and kicked ahead for another.
But all eyes remain on the battle to partner Hastings in the halves for round one against Canberra, with recruit Cogger and incumbent Tyson Gamble each playing 40 minutes.
Coming off the bench behind a starting Gamble, Cogger made an immediate impact when he kicked a 40-20 with one of his first touches.
The five-eighth then almost put Tom Jenkins over from the ensuing set, before the winger ran out of room on the right edge.
Cogger scored a try of his own in the second half, albeit in simple fashion after he chased down a kick from David Armstrong.
Fast footy as Cogger scores under the posts! 🧨— NRL (@NRL) #NRLKnightsSharks pic.twitter.com/rNL72RZdjwFebruary 17, 2024
Newcastle appeared to sign Cogger as their long-term five-eighth last August, when they lured him to the club on a three-year deal.
But Gamble's end to the season at the Knights has muddied the selection debate, after he and Hastings took them to a semi-final.
At the same time, Cogger was starring filling in at No.6 for Jarome Luai at Penrith, where he played a key role in the last 20 minutes of the grand final win.
Gamble had little to do in his first 20 minutes on the field on Saturday as both sides traded several early errors.
But his best moment came off the back of a bomb from Cogger, when he chased through to collect it and was held up over the line.
"We don't have to pick the team (yet). I'll use all the time I need," O'Brien said.
"We have another trial to work it out. We're fortunate we have very capable spine depth. We're relishing that. We've been on the other side of that.
"Cogs is a really steady head. He knows to kick you to good field position, hence the 40/20. He knows where to land the ball and set up our defence."
One major concern for Newcastle came in the form of an ugly concussion to centre Krystian Mapapalangi on the first tackle of the game, when his head collected Oregon Kaufusi's body.
With most of their top 17 not playing, Kaufusi made an early impact with a late offload for Cronulla's first try to Jayden Berrell.
The Sharks led 12-0 when Sione Katoa scored off a Jesse Colquhorn offload and subsequent Daniel Atkinson grubber kick, but from there it was all the Knights.
Cronulla forward Tom Hazelton could face a ban, after being sin-binned for a late high shot on Mat Croker.
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