Dundee United piled more pressure on Wilfried Nancy as they came from behind to condemn the Frenchman to a fourth straight defeat since becoming Celtic manager on another day of turmoil for the reigning Scottish champions.

Celtic looked to have responded positively to Sunday's League Cup final defeat thanks to Daizen Maeda's early goal, but second-half strikes from Krisztian Keresztes and Zac Sapsford turned the game in the struggling hosts' favour.

As eighth-placed United ended a seven-game run without a victory and an 11-year, 24-match wait for a win over the Glasgow side, Nancy becomes the first Celtic manager to have lost four games in a row since Jock Stein 47 years ago.

They remain six points behind Premiership leaders Hearts - albeit with a game in hand - on a day when Peter Lawwell announced he would be standing down as chairman citing "abuse and threats" from elements of their own their fans.

For all the talk of whether Nancy would retain his favoured 3-4-3 formation despite its early malfunctioning, it was Maeda being back to his best in his left-wing berth that ignited Celtic immediately from kick-off.

The speedy Japan forward had already left lumbering centre-back Bert Esselink in his wake several times before latching on to Johnny Kenny's flick behind the defence to fire into the far corner after 13 unfortunate minutes for United.

Kenny should have made it two soon after when he delayed his shot too long when clean through.

Celtic were threatening to blow United away, but Max Watters should have done better than to prod wide at the other end when the striker was found free in front of goal by Keresztes' misplaced shot.

Kenny missed from in front of goal following a low Maeda cross and United made Celtic pay as they played down the slope after the break.

Sapsford had already forced a good save from goalkeeper Kasper Schmeichel when substitute Vicko Sevelj set up Keresztes and the centre-half calmy placed a shot into the far corner.

As United piled on the pressure, striker Sapsford shaped an outrageous finish past Schmeichel as Celtic struggled to clear.

Maeda could have rescued at least a point late on but somehow headed against a post from all of six yards with the goal gaping on another dismal night for Celtic and their new manager.

After becoming the first Celtic manager to lose his first two games in charge before defeat by St Mirren at Hampden, Nancy aleady had a lot of work to do to win over the Glasgow club's expectant fanbase.

Chief executive Michael Nicholson insisted earlier in the day that the board's support for the former Columbus Crew head coach is "absolutely solid" despite a "disappointing" start, but how much longer can their patience continue?

The Frenchman made four changes - two of them enforced - but stuck to his guns with a shape that ensured Celtic were playing for high stakes at both ends of the pitch.

Luke McCowan in a left midfield role and Johnny Kenny, starting up front in place of the injured Kelechi Iheanacho, combined to unleash Maeda time and again.

However, with Liam Scales rested - and full-backs Anthony Ralston and Kieran Tierney flanking Auston Trusty - Celtic continue to look vulnerable at the back.

Whether it was United manager Jim Goodwin replacing the toiling Esselink with Sevelj at half time, or the fact they were shooting down the slope, the game turned.

Goodwin had recognised his own "need to start winning games" and lamented his side's tendency to lose late goals.

However, this time they held firm to ease pressure on himself and heap it on his opposite number, who has again been reminded that the Premiership is a world away from Major League Soccer.

Dundee United manager Jim Goodwin: "At half-time, we thought we were going to get opportunites. We had two or three half chances in the first half.

"It has been a long time since we beat Celtic in front of our own supporters and that's one for them.

"We are not getting carried away. We are not happy with our league position, but that gives us a lot of confidence."

Celtic manager Wilfried Nancy: "We lost the game in three minutes - two set-pieces that we conceded. Maybe the second one was offside before the corner.

"I think we did a good job - I think we had a good performance with all the opportunities we had in the first half.

"If we score the two or three tap ins we had, it would have been a different score."

United host Hibernian on Saturday, with Celtic entertaining Aberdeen on Sunday (both 15:00 GMT).