AC Milan turned up the heat further on Neil Lennon by recording a 3-1 victory over Celtic in their opening Europa League encounter
Lennon and his players came into the game with their backs against the wall after the 2-0 defeat to Rangers on Saturday and started poorly as Zlatan Ibrahimovic - at 39-years-old - ran the show at Celtic Park
Rade Krunic headed the Italians in front (14) before Brahim Diaz doubled the lead with a neat low finish (42)
Celtic improved after the break when switching to a back four and Mohamed Elyounoussi gave Lennon's team hope (75) but they were unable to fashion an equaliser
 Jens Hauge wrapped up the points in stoppage time as AC Milan stretched their unbeaten run in all competitions to 21 matches
Once again there were no fans allowed inside the stadium but Celtic started as if they were being cheered on by a packed house
However, they were hit by an Italian sucker punch
Castillejo drifted in from the right and flighted a cross in for Krunic to get in between defenders Stephen Welsh and Shane Duffy to direct his header past Vasilis Barkas
Celtic kept up a good tempo as they fought back but then the Serie A side began to occasionally flex their muscles and by the interval, they had doubled their lead
In the 42nd minute Ibrahimovic sent defender Theo Hernandez racing down the left and when he passed inside to Diaz, the attacker neatly side-stepped Duffy and Callum McGregor and slotted a shot low past Barkas
Lennon replaced Welsh and Leigh Griffiths with Elyounoussi and Ryan Christie for the start of the second half and went to a back four in a reshaped formation with some early joy
In the 51st minute, Celtic wing-back Diego Laxalt, on loan from the visitors, ended a promising move by driving just over the bar from the edge of the box
Tom Rogic replaced skipper Scott Brown in the 64th minute but it was another replacement, Elyounoussi, who gave Celtic a lifeline when he headed in from Christie's delivery
The home side gave it their all in search of a leveller but in the second minute of three added, Milan broke and Alexis Saelemaekers played in Hauge and his fellow substitute slipped the ball past Barkas
Ibrahimovic became the oldest outfield player to start a UEFA European match for AC Milan since Paolo Maldini, who was 40 years old when featuring against Weder Bremen in 2006
 And he proved that age really is only a number with a commanding performance, one that made his team tick from his role roaming free in the hole
 His awareness of players around him still is world-class as is his ability to pick a pass as shown by his ball in behind to kickstart the attack from which Dias doubled AC Milan's lead
 "I'm disappointed we lost
 I thought we deserved something from the game
 We were very good in the second half, a lot better, better play, better body language but we lacked a cutting edge
"We got into good areas in the first half but the final ball needs to be better at this level, we gave away two soft goals
"But we made changes at half-time and we played better in the second half
"It was markedly better than the weekend
 It was encouraging
 I don't like losing but there were a lot of good signs for me
"I wanted an improvement and we got a big improvement
 Part of me is quite pleased with that
"We could have shied away from it all after the criticism we have taken and I have taken but they showed their personality in the second half
"Celtic have a tricky trip to Aberdeen to negotiate on Sunday, a game live on  at 12pm
 They then play Lille next Thursday in their second Europa League fixture
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