Jay Stansfield scored his sixth league goal of the campaign for Birmingham
Birmingham City recorded impressive back-to-back 4-0 home wins as they beat high-flying Millwall at St Andrew's and ended the London side's unbeaten away record this season.
South Korean Paik Seung-ho scored his second goal in successive matches just before the half hour, with Demarai Gray netting just his second of the season on the stroke of half-time.
Alex Cochrane added a third goal four minutes into the second half and Jay Stansfield completed the rout with their fourth on 65 minutes.
The win made it three in four matches for Chris Davies' Birmingham side, who move up to ninth, just one point adrift of the top six. Millwall stay fourth in the table following their fourth league defeat of the season.
Birmingham were unsurprisingly unchanged from Saturday's home win over Portsmouth, with on-loan Sunderland winger Patrick Roberts passed fit to start, while Millwall made four changes following their 2-2 draw at Oxford United.
Both goalkeepers were tested in very wet conditions in the opening 25 minutes.
Millwall's Joe Cundle hit a thumping right-footed volley from the edge of the area , forcing Blues keeper James Beadle to palm it away, and Stansfield then forced Millwall's Max Crocombe to save low to his left with a shot from the edge of the area .
Blues opened the scoring just a minute later as Roberts, who impressed down the right wing all evening sent a cross the box, finding Paik, who fired it home into the bottom right corner.
Birmingham doubled their lead in the final minute of the first half when a heavy touch from Millwall's former Blues defender Wes Harding gifted the ball to Stansfield.
He exchanged passes on the edge of the box with German striker Marvin Ducksch before crossing for Gray to flick past a despairing Crocombe.
The home side added a key third goal just four minutes into the second half as Roberts again caused problems down the right and pulled it back for Tomoki Iwata.
His cross was headed out but only as far as Blues full-back Cochrane, whose fierce volley from the edge of the area took a slight deflection on the way through.
The influential Stansfield got his sixth goal of the league campaign when Iwata playing a short pass to substitute Keshi Anderson, who found Stansfield just outside the box and he controlled a bobbling ball before shooting past Crocombe to seal the victory.
Birmingham will take huge confidence into their game with third-placed Middlesbrough at the weekend.
Millwall's defeat, meanwhile, ended an impressive six-match unbeaten start on the road - they managed just two shots on target all evening, and next host Preston on Saturday lunchtime.
'Picked up from where we left off' - reaction
Birmingham City head coach Chris Davies told BBC WM:
"It was all about the hunger we showed tonight. It was a case of, you win a game 4-0 and it's very easy just to come off it just slightly. But I thought there was a relentlessness about us again.
"Really aggressive, really intense, really high tempo, players with the desire to score and arriving in the box, playing forward, running forward.
"We almost picked up exactly from where we left off in the previous game which is really pleasing, because it can easily go the other way. I was really pleased with that performance.
"Millwall are a solid, seasoned team at this level. They're always going to cause you a problem in a game, but I thought we managed it really well, we gave very little away, and we probably could have had more than the actual four that we scored in the end."
Chris Davies: 'It was all about the hunger we showed'
Millwall head coach Alex Neil told BBC London:
"We just weren't good enough on the evening. We've been good across most of the season so far, but tonight was a real disappointment for us.
"Timings of goals are always important. Conceding in the 45th minute and in the 48th minute is just horrendous timing. Just before half time, and just after half time.
"Credit to Birmingham , they were the better side, they deserved to win, we just didn't do enough"
"When goals go in, they get their tails up, the crowd gets behind them, our lads are a bit deflated, and that point I just wanted to make sure we didn't concede any more stupid goals, and keep some fresh legs for the weekend."
Player of the match
After the opportunity to rate players has closed, the score displayed represents the average from all the submissions by BBC Sport users.
