To make matters worse for the Eels, halfback Mitchell Moses suffered a suspected fractured eye socket early in Friday night's match and did not return for the second half.
"We're pretty sure he has a fractured eye socket," Eels coach Brad Arthur said.
"It was about the third minute. It was extremely tough of him to play on.
"He wanted to go back out there in the second half."
Broncos captain Adam Reynolds landed his 1000th NRL career goal to cap a memorable night for the hosts at The Gabba.
Parramatta were 'Walshed' in the opening stanza, like so many quality teams have been this year.
What has become clear in this 2023 season is that when the 21-year-old puts the foot down he is nigh on unstoppable.
His speed, passing game, step and vision on the field is rare in any player, let alone someone so young. Walsh showcased all of those qualities to inspire Brisbane to a 24-0 halftime lead.
Walsh finished with five line break assists, two line breaks, a try assist and a late try.
The Broncos are joint-leaders with Penrith on 38 points and all but assured of a top-two finish.
Broncos coach Kevin Walters said his side's best was yet to come.
"I don't know where the cap for our side is," he said.
"To be fair, Parramatta had their injury problems. They had to reshape their defensive line which is always difficult when you have got guys like Reyno and Walshy pulling the strings."
The Eels are on 26 points, two points outside the top eight, and still have to play the Panthers in the penultimate round of the competition.
Brisbane's first try was electrifying, after they had defended their line against an early Parramatta onslaught.
On the fifth tackle, Walsh spied a chance on the short side. He accelerated, found second-rower Kurt Capewell who kicked off the outside of his right foot to perfection for Reynolds to collect, step and score.
Hooker Billy Walters stepped twice off his left foot near the line to score the Broncos' second. Then Walsh lit up The Gabba with a 20m pass that soared through the air and right into the breadbasket of winger Deine Mariner who went over untouched.
On the cusp of halftime Mariner latched onto an intercept 10m out from his own line, raced away and found centre Herbie Farnworth with a one-handed offload.
Farnworth was tackled by Eels halfback Mitchell Moses, got up and ran the last 10 metres backwards for laughs to score. It was a statement by the freewheeling home side.
Mariner scored his second thanks to some Reynolds and Ezra Mam magic. Mam dazzled his way over and Mariner put another outside of the foot kick in for Walters to get his double as the carnage continued.
Parramatta winger Sean Russell and their best player, No.6 Dylan Brown, both scored in the second stanza.
Veteran Eels forward Andrew Davey was concussed in the second half and helped to his feet by Brisbane duo Kotoni Staggs in a show of sportsmanship, before Parramatta bench forward Wiremu Greig was put on report for a head slam on Keenan Palasia.
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