Boer has been sidelined for much of the season because of a troublesome toe injury that badly damaged the tendons running beneath his foot after suffering the setback against Northampton back in September.
"It has been a frustrating injury but it is getting back to normal," Boer said. "I got jumped on and the pressure extended the joint around the tendon and it was very uncomfortable.
"I couldn't put any major pressure down on it and for someone who doesn't get injured too often, it was extremely frustrating."
However, he made his return last Saturday from the bench and is relishing the prospect of clashing with his former club as he told www.gloucesterrugby.co.uk. "The Premiership can be a cruel place sometimes. If you lose one game in five or six you are doing okay, but if you lose two from five you suddenly find yourself in mid-table rather than the top four.
"This is a very big game for us and I am just thrilled to be back and involved. It has been very frustrating looking from the outside in and now I just want to get back out there.
"We all felt that losing to Leicester was a huge disappointment because it was a game we should and could have won and now we need to try and get back in form this weekend."
Boer will start on the openside in place of Hazell who has been rested by head coach Dean Ryan following an outstanding series of performances and heavy involvement with the England squad who are preparing for the visit of the All Blacks tomorrow.
"Andy simply needs a break," Ryan confirmed. "He has worked exceptionally hard, not only with us but with England, and we need to ensure he is managed properly at this stage of the season. A break should really help him."
The inclusion of Boer is one of six changes to the team that lost 25-20 to the Tigers. Quinton Davids returns to the second row in place of Peter Buxton who switches back to the number six position in place of Adam Balding.
James Parkes gets a run at hooker because Mefin Davies is on international duty with Wales. It also means that Olivier Azam will return from the shoulder injury he sustained against Bristol back in September to sit on the bench.
There are also three changes in the backs. Haydn Thomas starts at scrum-half in place of Peter Richards, Marcel Garvey will feature in a Premiership match for the first time this season in place of Mark Foster, while Terry Fanolua gets a run in the centre in place of Anthony Allen, who moves to the bench.
But Boer is warning of a titanic battle on Sunday at the Madejski Stadium. "London Irish have always been very effective at what they do - they do the basics well, have a big set piece, are a great scrapping side and can cause havoc against almost anybody.
"At home they can be as dangerous as Sale, Wasps or Leicester and we have to be fully switched on against them. It should be a really good match.
"It is a tough place to go and play but we are looking forward to a massive challenge."
GLOUCESTER (v London Irish, Sunday, Madejski Stadium 3pm): Olly Morgan; Rob Thirlby, James Simpson-Daniel, Terry Fanolua, Marcel Garvey; Ludovic Mercier, Haydn Thomas; Patrice Collazo, James Parkes, Gary Powell, Adam Eustace, Quinton Davids, Peter Buxton (capt), Jake Boer, James Forrester. Reps: Olivier Azam, Nick Wood, Jonathan Pendlebury, Adam Balding, Peter Richards, Anthony Allen, Brad Davies.