Merrick, who was the A-League's most experienced coach and led the club to the 2017 Grand Final, was sacked following two wins from his first 11 games, with 25 goals conceded.

His interim replacement, Deans, will take charge for this Friday's contest against runaway leaders Sydney FC, alongside A-League assistant Qiang Li.

A former Newcastle Jet, Deans is the W-League's most experienced coach with five years at the helm, winning the 2015-16 W-League Coach of the Year. 

It's unclear how Deans' new, albeit temporary, dual role will affect both teams, with Newcastle's W-League side set to face Adelaide United at 5pm this Friday, immediately before Newcastle play Sydney in the A-League.

"During Ernie's tenure, the club reached its first Grand Final in more than 10 years and we're grateful for his contribution during his two and a half years in Newcastle," Jets chief executive Lawrie McKinna said in a statement.

"However, results and performances haven't been good enough this season and a change was needed.

"On behalf of everyone at the club, I wish Ernie all the best in his future endeavours."