Tommy Smith's controversial late penalty rescued a draw for Derby after Hull looked set to complete a Coca-Cola Championship double at Pride Park.
Smith netted for the third straight game after referee Andy D'Urso adjudged Scott Wiseman to have pushed Paul Peschisolido in the box.
It cancelled out Stuart Green's spectacular first-half volley, the midfielder's second goal against the Rams this season after he netted the winner in October's reverse fixture.
With both sides securing league safety with weekend draws, a certain amount of tinkering with personnel was to be expected.
But Hull made five and Derby an amazing seven changes from Saturday, the Rams handing a debut to academy defender Miles Addison.
He started alongside fellow 17-year-old Lewin Nyatanga, forming what is thought to be the youngest centre-back partnership in the club's history.
Neither were particularly tested early on but nor were the visitors' pairing of Leon Cort and Damien Delaney as both sides cancelled each other out.
Jon Parkin should have changed all that for Hull after Stuart Green released Craig Fagan down the left wing, but the giant striker ballooned Fagan's low cross over the bar.
The lively Fagan then screwed wide from range while at the other end Smith had the first shot on target with a mishit drive.
Delaney had to be on his toes to stop Peschisolido being played in, before the Canadian striker virtually replicated Parkin's miss from Lee Holmes' left-wing cross.
Peschisolido was no closer with a 25-yard half-volley although the Rams were starting to press and a wonderful diagonal ball from Inigo Idiakez found Morten Bisgaard free in the box, but poor control allowed Alan Rogers to intercept.
Considering the youth of their centre-halves it was ironic that two of Derby's most experienced campaigners conspired to help Hull take the lead.
Idiakez and skipper Michael Johnson got in each other's way trying to head the ball clear and it fell to Green, whose half-volley flew into the top corner from 20 yards.
Despite the disappointment of falling behind, the first home game since chairman John Sleightholme's resignation saw no repeat of the "sack the board" chants that have been a feature at Pride Park this season.
Idiakez almost atoned for his earlier error with a free-kick a minute into the second half that dipped just too late.
The Spaniard had a second chance minutes later from slightly closer in, but this time he scuffed his shot straight at goalkeeper Boaz Myhill.
Peschisolido had two bites of the cherry after a good ball from Smith but his first shot was blocked and his second trickled through to Myhill.
Rams boss Terry Westley threw on Richard Jackson, Adam Bolder and Giles Barnes but the most they could earn was a series of corners which came to nothing.
The frustration got too much for Idiakez who escaped a booking despite kicking out at Fagan.
Moments later and Parkin's close-range volley hit the back of Addison, Cort heading the resulting corner over the bar.
At the other end, Bolder was beginning to find Smith with alarming regularity on the left wing and Smith's low cross had to be scrambled clear following Myhill's fumble.
Hull would have killed the game but for Lee Camp's brilliant fingertip save from Green and Bisgaard's clearance off the line from Cort's header.
Substitute Kevin Ellison forced another fine stop from Camp and yet another towering Cort leap saw another header sail over.
Just as the visitors looked set for their first win at Derby since 1968, Wiseman became the victim of a highly contentious penalty decision by D'Urso.
After vehement protests from the Hull players, Smith stepped up to despatch the spot-kick low to Myhill's left.
Teams
Derby: Camp, Edworthy, Nyatanga, Michael Johnson (Jackson 57),Addison, Smith, Bisgaard, Thirlwell (Barnes 64), Idiakez,Holmes (Bolder 64), Peschisolido.
Subs Not Used: Poole, Ashton.
Goals: Smith 89 pen.
Hull: Myhill, Wiseman, Cort, Delaney, Rogers, Green, Andrews,Welsh, Paynter (Ellison 70), Parkin, Fagan (Duffy 90).
Subs Not Used: Duke, Thelwell, Fry.
Goals: Green 33.
Att: 24,961
Ref: A D'Urso (Essex).