The Lions are eight points better off than City, but like their opponents they have little left to play for in the remaining week of the regular season.
Gary Rowett's side had a slim chance of reaching the playoffs with four games to go thanks to successive victories over Middlesbrough, Rotherham United and Stoke City.
However, the South London side have since taken one point from the last 12 on offer and are now effectively battling for a top-half finish.
Rowett will be disappointed with his side's recent form, having lost by three goals at home to Swansea City and Bournemouth, as well as going down 1-0 at Watford last time out.
The Lions' only point since April 5 came in a goalless draw with Brentford, though not since under Neil Harris in March 2019 have they lost three league games in a row.
While Millwall can finish as high as eighth if results go their way, the best Bristol City can hope for is a 13th-place finish, though even that looks highly unlikely.
The Robins have endured a poor campaign, with experienced boss Nigel Pearson not quite being able to turn things around at Ashton Gate.
Still, reports this week suggest that Pearson - currently under contract for two more games - will be handed a three-year deal by City in the coming days.
City have games with Millwall and Brentford to conclude the campaign, but focus will already be on the summer window as 13 players - and Pearson - are out of contract next month.
Pearson's side are winless in eight matches, losing the last two of those 2-1 to Wycombe Wanderers and 3-2 at home to Luton Town.
City have performed better on their travels this term, with their return of 27 points from 22 away games one point less than Millwall have accrued in the same number of home games.
The Robins have already won at The Den this season, in fact, prevailing 3-0 in January's FA Cup fourth-round tie.
That is not likely to be at the expense of Nakhi Wells, who has netted six goals in nine games against Millwall in all competitions.
Millwall possible starting lineup:
Bialkowski; Evans, Pearce, Cooper; Romeo, Wallace, Kieftenbeld, Mitchell, Malone; Zohore, Bennett
Bristol City possible starting lineup:
Bentley; Hunt, Vyner, Kalas, Rowe; Lansbury, Nagy, Bakinson; Semenyo, Wells, Palmer
We say: Millwall 1-1 Bristol City
Both sides are in bad form and have little left to play for on the face of it heading into the penultimate round of fixtures.
Millwall won the reverse fixture 2-0, but they have not completed a league double against City since 1992-93 and we can see that run being prolonged with a draw here.