On-the-whistle report: Will Grigg and Millers inflict derby humiliation ... Doncaster Rovers 0 Rotherham United 6

The loan hot-shot got in on the action in the second half after a three-goal blitz from the Millers had killed the EFL Trophy group-stage clash early on at the Keepmoat Stadium.

With the damage already done, Rotherham cantered home in the second half and their margin of victory could have been even greater.

As in the League One game at AESSEAL New York Stadium late last month - won 2-0 by the home side - Doncaster played some decent stuff at times but the Millers were just bigger, stronger and faster when it mattered.

There was also a debut goal for teenager Jake Hull on a balmy night when the visitors gave first outings to five players.

The opening shot came with only five seconds on the clock as Kieran Sadlier drove forward from the kick-off and tried his luck from 20 yards, giving Louis Jones an easy save.

After the Rovers old boy had slammed another effort wide, Rotherham suddenly swept into a 3-0 lead.

First, Mickel Miller's 13th-minute intended cross to the back post floated over Jones and into the roof of the net, then two minutes later Freddie Ladapo took Dan Barlaser's pass, rounded the keeper and coolly slotted the ball home.

Seconds afterwards, Hakeem Odoffin left the crossbar shaking with a stunning effort from distance and poor old Jones was picking the ball out of his goal when the rebound hit him and bounced over the line.

Doncaster tried to respond and Matt Smith was guilty of a glaring miss, firing the ball over the bar, before Ben Close forced a save from Josh Vickers.

Grigg had yet to really get into the game but must have been licking his lips at the prospect of the chances that might be coming his way as the match unfolded.

The striker's first opportunity arrived just after the half-hour mark but it was a difficult one and, leaning back, he could only direct it over the bar.

Away fans had been chanting 'We want four' and the Millers almost obliged as another debutant, Tolaji Bola, showed up well down the left. He delivered an inviting cross and Ladapo's header flashed just wide.

Half-time was approaching and Doncaster wasted another golden chance to cut the deficit, Jordy Hiwula being sprung clear by Tommy Rowe's pass only to fail to hit the target.

Rotherham had gone with a relatively strong side, handing debuts to goalkeeper Vickers, centre-half Hull  and Bola as well as Grigg. Jacob Gratton entered proceedings after the interval to complete the list of debutants.

It was a special day for Vickers especially as he'd had to wait for more than a season for his first start.

Sadlier was selected against his former side having tormented Rovers at New York - and did so again - while senior players like Joe Mattock, Barlaser and Ladapo were also included.

Grigg's moment came four minutes after the break when Ladapo's shot hit the post and gave the deadline-day signing a simple tap-in.

The Millers took complete control of the second half and Ladapo was unlucky to see a clever effort clip the bar as Paul Warne's men poured forward.

It needed fingertip heroics from Jones to keep out Mattock's free-kick before Miller fired over from the edge of the penalty area and then Jones did well again to parry Ladapo's diving header from another Bola supply.

Goal number five arrived on 67 minutes, making it a dream debut for Hull as the teenager appeared to get the crucial touch on Barlaser's corner.

After substitute Michael Smith head headed over, both teams were reduced to ten men in the 79th minute as, with all substitutions having been made, Rovers' Ben Close was struggling and the Millers offered to sacrifice Bola to keep the numbers even.

The home side's humiliation was compounded by chants for more goals from a vociferous away following and Mattock duly obliged with an 85th-minute header from Miller's corner.

Another sub, Ollie Rathbone, almost added a seventh in stoppage time.

Grigg on fire. Rotherham on fire.

Doncaster (4-3-3): Louis Jones; Charlie Seaman, Branden Horton, Ro-Shaun Williams, Tommy Rowe; Matt Smith, John Bostock, Ben Close; Rodgrigo Vilca (Dan Gardner 63), Joe Dodoo (AJ Greaves 63), Jordy Hiwula (Kyle Knoyle  63). Subs not used: Liam Ravenhill, Ethan Harrison, Tavonga Kuleya.

Rotherham (3-5-2): Josh Vickers; Rarmani Edmonds-Green, Jake Hull, Joe Mattock; Mickel Miller, Dan Barlaser, Kieran Sadlier (Rathbone H-T), Hakeem Odoffin, Tolaji Bola; Will Grigg (Jacob Gratton 65), Freddie Ladapo (Michael Smith 65). Subs not used: Viktor Johansson, Michael Ihiekwe, Ben Wiles, Jamie Lindsay.

Goals: Miller 13, Ladapo 15, Jones og 16, Grigg 49, Jake Hull 67, Joe Mattock 85 (Rotherham).

Referee: Ben Speedie (Merseyside).

Attendance: 1,765.