South African fast bowler Hardus Viljoen rescued Derbyshire with the bat on a keenly contested opening day at Derby.
Viljoen (pictured) scored his first 50 for the county as the home side recovered from 167 for 7 to 265 and then reduced Middlesex to 45 for 3 at the close.
Ravi Rampaul and Duanne Olivier claimed their maiden wickets for Derbyshire as Max Holden and Robbie White went cheaply before Viljoen removed Hilton Cartwright.
Despite bright sunshine, it was no great surprise after so much recent rain that Middlesex elected to bowl but their seamers, with the exception of Tim Murtagh, lacked consistency before lunch.
Murtagh had Luis Reece brilliantly caught by Ollie Rayner at second slip in the seventh over but Ben Slater and Wayne Madsen played well until Slater left one from Harris that moved in to take the off-stump.
Cartwright had Alex Hughes caught behind off the last ball of the morning but it had still been a good session for Derbyshire although the picture quickly changed after lunch.
Billy Godleman drove a cut Harris for consecutive fours but was beaten by some late movement and Madsen was defeated by Murtagh’s inswing before Gary Wilson mistimed a pull to mid-wicket.
But Viljoen and Tony Palladino grew in confidence against an attack that was without Toby Roland-Jones after lunch because of slight soreness in his back.
Viljoen became increasingly assertive and raced to his first half century for Derbyshire by dispatching Rayner for three sixes from five balls before Harris claimed his fourth wicket when Palladino was caught at second slip on the stroke of tea.
Helm was hooked by Viljoen for a fourth six but the paceman wrapped up the innings off consecutive balls courtesy of two more catches by Rayner.
Derbyshire’s total looked even more competitive when Holden edged a loose drive at Ravi Rampaul and the quality of Derbyshire’s bowling forced Sam Robson and White to fight for survival before Olivier claimed his first wicket for the county.
Only 22 runs were scored in 13 overs, 11 of them extras, and the pressure told when White followed one that swung away to be taken at third slip.
Robson was determined to see his side through to stumps but Cartwright was lured into edging a drive to second slip as Derbyshire ended the day on top.