Oates has only managed nine games this season, struggling with injury, and is yet to find the try-line in those games.
Despite that, his running game has still been at an elite level, averaging close to 200 metres per game with the ball in hand, a stat which has put Brisbane onto the front foot in the games he has played.
Arthars has had a strong season for Brisbane, scoring 8 tries in his 17 games, although he has averaged under 100 metres per game.
Lockyer said the fact Arthars is quicker and more nimble played into the decision.
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"It would have been enormous given what Corey's done for the club," Lockyer said on Wide World of Sports' QLDER.
"Remember, he's just come back, he hasn't had a lot of luck with injuries this year, so he hasn't really had a lot of continuous football," Lockyer added, referring to the knee injuries that have hampered Oates' season.
"I think what it comes down to is mobility. Corey brings the ball back well, but (the Storm have) got a couple of big, mobile wingers ... and maybe in the last couple of weeks there would have been a few moments where they thought Jesse was just a bit more nimble or quicker to the situation, quicker to defuse the situation."
Further complicating the situation for Oates is the fact he is currently uncontracted for next year and has reportedly not yet decided to remain with Brisbane, who have asked him to take a pay cut yet again to remain at Red Hill.
The Broncos will clash with the Storm on Friday evening at Suncorp Stadium, with the winner advancing to the preliminary finals, while the loser will have to play a Week 2 semi-final against the winner of Saturday's clash in the Shire between the Cronulla Sharks and Sydney Roosters.