Joe Gallen will be placed in caretaker charge of Portsmouth, as announced by their official club website.
He will be assisted by first team coach Jake Wigley starting on Thursday.
Portsmouth boss Kenny Jackett is taking a break from the dugout at Fratton Park following a medical procedure that will require a short period of rest and recuperation.
Pompey’s official club statement reads: “We wish Kenny a speedy recovery and look forward to seeing him back shortly.”
Gallen, who is 48 years old, will lead the League One promotion hopefuls for now. He has been their assistant to Jackett since 2017 and has worked under him in the past at Millwall, Wolves and Rotherham United.
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The former Republic of Ireland youth international spent his playing career with the likes of Watford, Exeter City and Dundalk before hanging up his boots in 1998.
He has since delved into the coaching world and got his first role in the academy set-up at QPR. He spent nine years with the Hoops working in a couple of different positions before leaving the London club in 2007 to become the assistant manager of Exeter.
Gallen then linked up with Jackett at Millwall shortly after and has stayed with him ever since.
The number two will now take charge of Portsmouth, alongside Wigley, on a temporary basis. They are in action tomorrow night against Bristol Rovers away followed by a home fixture against Blackpool on Saturday.