Patrick McClean is ruled out while Ryan McBride, Aaron Barry, Dean Jarvis and Conor McDermott are all struggling to be fit and face late fitness decisions.
Derry lie third in the table, six places above their opponents.
The Candystripes have taken just one point from the previous two league matches between the sides this season.
"I respect Finn Harps immensely and I expect it to be a fantastic derby occasion," said Shiels.
"Their manager Ollie Horgan has done a fantastic job on a limited budget. They will go into the game with no fear but it's of paramount importance that we win.
"I'm always loathe to predict the outcome of derby matches as there are so many twists of fate involved and so many things can go against you, including the rub of the green with decisions."
The Brandywell men face an important encounter with second-placed Cork City on Monday night but the Derry boss is keen to adopt the old maxim of 'one game at a time'.
"I always say that the most important game is your next one so we will be concentrating solely on Finn Harps to begin with.
"We will just drive on and hope that our luck changes a bit in terms of performance and outcomes.
"We have played well in our last three games but only took a point apiece from the clashes with Sligo Rovers and St Patrick's Athletic, and lost to Limerick."
There will be live commentary of the game on BBC Radio Foyle 94.1FM and the BBC Sport website from 20:00 BST.

Aguero has until 18:00 BST on Thursday 1 September to respond to the charge.
If found guilty, the Argentina international faces a three-match ban.
He would miss Premier League games with Manchester United on 10 September and Bournemouth on 17 September.
The 28-year-old would also miss the EFL Cup third-round game against Swansea.
Referee Andre Marriner did not see the 76th-minute incident during City's 3-1 win on Sunday and the FA has decided to take retrospective action after reviewing television footage.
Aguero is currently out of Argentina's two World Cup 2018 qualifiers next month with a calf injury.

He is currently director of the University of Toronto's Munk School of Global Affairs.
The Canadian academic, with an expertise in international law, was a postgraduate student at Cambridge in the 1980s.
Prof Toope will take over in October 2017, when the current vice-chancellor, Sir Leszek Borysiewicz, steps down.
The new Cambridge head, whose appointment will have to be approved by the university's governing body, is a former vice-chancellor of the University of British Columbia.
His academic work has specialised in human rights and international dispute resolution, and he has worked for the UN Working Group on Enforced or Involuntary Disappearances.
Prof Toope will be the 346th person to hold the office, in a role dating back to 1412.
He said: "I am thrilled to be returning to this great university.
"I look forward to working with staff and students in the pursuit of academic excellence and tremendous international engagement."
Derry City have injury concerns over a number of players ahead of their Premier Division derby against Finn Harps at Finn Park on Friday night.
[NEXT_CONCEPT]
Manchester City striker Sergio Aguero has been given an extra 24 hours to argue his case after being charged with violent conduct by the Football Association for elbowing West Ham's Winston Reid.
[NEXT_CONCEPT]
Stephen Toope has been chosen as the next vice-chancellor of the University of Cambridge.