Frokjaer joins midfielders Ali McCann and Brad Potts, as well as goalkeeper Freddie Woodman, on the sidelines.
Preston have won just one of their past 13 league games, a run which has left them only three points clear of the relegation zone but boss Paul Heckingbottom believes his side have the fight to steer clear of trouble.
"I wouldn't question their application or attitude," he told BBC Radio Lancashire.
"I can't have people criticise the players when they are working as hard as ever - the lads have been let down by other factors."
After Saturday's meeting with Plymouth, Preston finish their campaign at Bristol City.
Pick of the stats: Preston North End v Plymouth Argylepublished at 10:09 25 April
10:09 25 April
Both these sides still have work to do to secure their Championship status.
Plymouth will start Saturday's game (15:00 BST) three points short of safety, while Preston's six-match winless run means they are only three points clear of trouble.
Preston are unbeaten across their past six league games against Plymouth (W3 D3), since a 1-0 away loss in October 2008.
Plymouth are winless in their past seven away league games against Preston (D3 L4), since a 1-0 win in November 1997.
Preston have won just one of their past 13 league games (D6 L6), losing the past three in a row. They last lost more consecutively between April and August last year (seven).
Plymouth have alternated between victory (three) and defeat (two) in their past five league games, beating Norwich last time out. However, both losses in that run have come away from home, while all three victories have come at home.
Pick of the stats: Queen's Park Rangers v Burnleypublished at 10:07 25 April
10:07 25 April
Having secured automatic promotion, Burnley will continue the battle for the title when they visit Queen's Park Rangers on Saturday (12:30 BST).
The Clarets won promotion after defeating rivals Sheffield United on Monday but now turn their attentions to winning the league.
They are currently in second place but level on points with Leeds United, bested only by goal difference.
However the title is not the only thing the Lancashire side are vying for, they could also match Reading's unbeaten Championship record if they keep themselves undefeated across their final two league games.
QPR have won just one of their last seven home league games against Burnley (D3 L3), a 2-0 victory in the Premier League in December 2014.
Burnley have kept a clean sheet in four of their last five league games against QPR, with the exception being a 2-1 home loss in April 2023.
After winning seven of their eight home league games between December and February (L1), QPR are now winless in their last five at Loftus Road (D3 L2).
Burnley are unbeaten in their last 31 league games (W20 D11). It's their longest run in their league history, while only Reading (33 in 2005-06) have had a longer run in a single second tier campaign.
Burnley have conceded just 15 goals in the Championship this season, despite having an xG against figure of 36.3. Their record of conceding 21 goals fewer than their xGA suggests is at least 10 more than any other side this season.
'Survival is key in first Premier League season'published at 17:23 23 April
17:23 23 April
David Unsworth Former Burnley defender on BBC Radio Lancashire
Image source, PA Media
Image caption,
Burnley boss Scott Parker celebrates after the win over Sheffield United sealed promotion
What does success look like for Scotty Parker next year in the Premier League? If he survives the first season, it's a brilliant season. Survival is key.
You only have to look at clubs that are promoted; they usually go straight back down.
Celebrations quickly turn into a survival campaign. That's how you build a club. That's what Sean Dyche did. Stay in the Premier League the first year and build from there.
I hope he [Parker] is backed in the transfer market in terms of recruitment and given the money that he deserves because he is a fine, fine young manager.
I knew Scotty Parker was a good young coach, but I didn't realise how good he actually was until he came to this football club.
He's a young man with great experience already. He's got three promotions under his belt, and the sky is the limit for him.
He should be getting amazing plaudits. I don't think he does. I don't think he gets the acclaim and the plaudits that he is due.
The way he's turned it around in a short period and then from January, it's incredible.
If this guy is not up for manager of the year, there is something wrong.
'Burnley are set up better for Premier League now'published at 11:04 23 April
11:04 23 April
Image source, PA Media
We asked you how it feels to see Burnley win promotion back to the Premier League and whether they can stay up next season.
Here's what you said:
Alan: For a mostly new squad to achieve what they have done is beyond belief. The whole club have been magnificent in giving supporters a team to get behind and believe in again. Superb.
Tom: This promotion feels completely different to last time. Last time, it felt as if the plan was to get promoted after a few seasons in the Championship rebuilding and preparing. This time it definitely was the plan. I feel we are much better set up for the PL now. Our defence is so solid so hopefully we can grind out the results next season. I hope Parker's backed financially in the summer to buy a proper striker otherwise we're in trouble.
James: It's such a mixed bag. It's absolute elation in the moment, especially considering the turbulence at the start of the season in terms of new manager and the exodus. On the other hand, it's tinged with looking up the record of the most recently promoted teams and the experience of last year. The gulf is only getting bigger and it'll take something Herculean to stay up now we're back.
Joe: It's a great feeling to secure the promotion, but a bit apprehensive for next season. Our last run in the Prem was miserable. Scott Parker's style will be more suited in the Prem but seeing how the promoted teams have got on this year doesn't inspire much confidence.
Frank: Defensively Scott Parker has done an incredible job. To go 31 games undefeated in this league has been an awesome achievement, conceding only 15 goals all season thus far. Like all clubs, Burnley need a reliable high-scoring striker (or two!) - their top scorer with 15 goals, Brownhill, plays in midfield, and this lack of goals from the front men will be a major issue next season in the Premier League. Burnley's location to the Manchester clubs and good relationships may help them get quality loanees from either club which would help from both a quality and financial aspect. I think Burnley have a good chance of surviving next season.
Richard: Burnley should do better than Leeds in the Premier League next season if they can keep hold of Parker and back him. Good luck and congratulations. East Lancashire needs a settled Premier League club.
Matt: Consistency and defensive brilliance all season and the winning results have started to come. They have deserved promotion - not forgetting Sheffield United had a two-point deduction. Burnley have had a massive transition with 50+ ins and outs. Remarkable what Scott Parker has achieved. We need strength in depth across the defence and midfield, we need a number 9 who is going to get 15+ goals a season. Survival in 17th place has to be the aim.
Clifford: We were incredible, fulfilled our objective, breaking records on the way. People say we are boring. Football has become a tad boring. Scott Parker has been quite simply amazing.