The Bluebirds lost 1-0 to Coventry City on Wednesday to make it one win in eight, while Luton played out a third successive draw in midweek and remain in the top half.
"Disappointment" was a word used on three occasions by Harris when reflecting on Cardiff's defeat to lowly Coventry, with the Bluebirds producing another terrible display.
Tyler Walker profited from a mix-up at the back for the only goal of the game as Coventry picked up a deserved victory at St Andrew's.
Since appearing to turn their season around with a vital 3-0 win over Barnsley at the start of the month, Cardiff have now taken one point from the last nine on offer.
That includes losses to Coventry and Severnside rivals Bristol City without scoring, either side of a 1-1 draw away at Harris's former club Millwall.
Another setback for the Bluebirds this weekend and the club hierarchy may well decide to bring Harris's year-long tenure to an end.
Luton head to the Welsh capital seeking a first win in four, having drawn their last three matches by the same 1-1 scoreline.
The Hatters now embark on back-to-back away games in Wales and will be looking to build on an impressive record on their travels.
They have lost just two of their last 16 away league games under Blaenrhondda-born coach Jones, keeping nine clean sheets, and no Championship side has picked up more away wins post-lockdown in June.
Cardiff City Championship form: DLWLDL
Luton Town Championship form: DLWDDD
Josh Murphy returned to Cardiff's starting lineup for their only change against Coventry, but he failed to make much of an impression and may be replaced here.
Cardiff City possible starting lineup:
Smithies; Bacuna, Morrison, Nelson, Bennett; Vaulks, Pack, Harris; Wilson; Moore, Glatzel
Luton Town possible starting lineup:
Sluga; Pearson, Bradley, Rea, Norrington-Davies; Berry, Dewsbury-Hall, Mpanzu; Cornick, Collins, Lee
We say: Cardiff City 0-1 Luton Town
Cardiff are unbeaten in five league meetings with Luton since 2005 and have won their last two home encounters.
The Hatters enter this game in better form, though, and they have tended to perform better on their travels than at home, so we are going with a narrow away win.