Match ends, Ipswich Town 0, Derby County 1.
Tom Ince's fourth goal in five days saw Derby beat Ipswich to move up to second in the Championship.
Having scored a hat-trick in a 4-0 win over Bristol City on Tuesday, Ince struck again on 40 minutes after being put through on goal by Johnny Russell.
Ipswich had chances to equalise, with Daryl Murphy and Jonathan Douglas both going close with headers.
But Derby held on to move a point above Brighton, who lost 3-0 at home to leaders Middlesbrough.
Ipswich remain in the final play-off spot, one point ahead of Birmingham City, and Saturday's defeat was their third at home this season, all of them by promotion rivals.
The hosts will feel frustrated to have lost what was a scrappy game in which they had opportunities to find the net.
Freddie Sears had the first real chance of the match, when his low shot was easily saved by Lee Grant.
Bradley Johnson then went close for Derby with a curling shot from 20 yards that went just wide, before Town defender Tommy Smith denied Chris Martin with an excellent block in the area.
George Thorne then blocked a Sears attempt at the other end before Jacob Butterfield saw a long-range shot saved by Ipswich keeper Dean Gerken.
Ince fired the Rams in front after being fed the ball by Russell, who was under pressure from Christophe Berra, when just inside the box and with only Gerken to beat.
Ipswich pressed for an equaliser after half-time with a Sears cross finding Murphy, whose header drifted narrowly over the bar.
Substitute Ryan Fraser's shot from the edge of the box was blocked by Jason Shackell and Douglas went very close to levelling for the hosts when his header at goal was cleared off the line by Butterfield.
Sears also fired wide from a tight angle as Derby held on to extend their unbeaten run to six games.
Ipswich boss Mick McCarthy: "It was a good, closely-fought game with not a lot in it. I have no complaints about the performance, only a few complaints about the goal as we had the ball and it ended up in our goal.
"There were times we could have picked a better pass or had more composure but I'm not going to criticise my players.
"You have to give Derby a lot of credit. If anyone finishes above them and Middlesbrough, I would be very surprised."
Derby head coach Paul Clement: "We had to cope with their aerial onslaught, but I thought our centre-backs were outstanding. It was a proper man's performance and I am absolutely delighted.
"Tom has had a good week and took his goal well. But I am really pleased with his physical effort off the ball. He is a real team player and that is an excellent quality to have.
"This is such a difficult place to come and it was one of our hardest, and most physical, games of the season. It was a massive three points for us."
- 6BerraBooked at 26mins
- 7Maitland-NilesSubstituted forBruat 63'minutes
- 22DouglasBooked at 68minsSubstituted forVarneyat 84'minutes
- 11PitmanSubstituted forFraserat 58'minutes
- 18ButterfieldBooked at 76minsSubstituted forHendrickat 83'minutes
- 23InceBooked at 81minsSubstituted forBairdat 90+4'minutes
- 11RussellSubstituted forWeimannat 79'minutes
- Keith Hill
- Shots on Target
Second Half ends, Ipswich Town 0, Derby County 1.
Substitution, Derby County. Chris Baird replaces Tom Ince.
Corner, Derby County. Conceded by Dean Gerken.
Attempt saved. Bradley Johnson (Derby County) left footed shot from outside the box is saved in the top left corner. Assisted by Andreas Weimann.
Offside, Ipswich Town. Jonas Knudsen tries a through ball, but Freddie Sears is caught offside.
Substitution, Ipswich Town. Luke Varney replaces Jonathan Douglas.
Substitution, Derby County. Jeff Hendrick replaces Jacob Butterfield.
Attempt missed. Freddie Sears (Ipswich Town) right footed shot from a difficult angle on the right misses to the left. Assisted by Ryan Fraser following a corner.
Corner, Ipswich Town. Conceded by George Thorne.
Tom Ince (Derby County) is shown the yellow card for a bad foul.
Ryan Fraser (Ipswich Town) wins a free kick on the left wing.
Foul by Tom Ince (Derby County).
Attempt blocked. Jonathan Douglas (Ipswich Town) header from the centre of the box is blocked. Assisted by Ryan Fraser with a cross.
Corner, Ipswich Town. Conceded by Cyrus Christie.
Substitution, Derby County. Andreas Weimann replaces Johnny Russell.
Jacob Butterfield (Derby County) is shown the yellow card.
Cole Skuse (Ipswich Town) wins a free kick in the defensive half.
Foul by Jacob Butterfield (Derby County).
Corner, Derby County. Conceded by Jonas Knudsen.