Celtic didn’t suffer a European hangover as goals from Gary Hooper and Victor Wanyama saw the SPL champions comfortably defeat Dundee 2-0.
After dropping points in the their last two league games against Hibernian and St Johnstone, the victory puts the Hoops' title charge back on track.
Neil Lennon made two changes from Wednesday's goalless draw in the Champions League against Benfica, with both Mikael Lustig and Miku making way for Lassad and Hooper, while his opposite number Barry Smith had to replace Lewis Toshney, who is on-loan from the Parkhead side for Kyle Benedictus.
The home side looked to gain an early advantage in the game with Charlie Mulgrew going close from a free kick just outside the box and James Forrest's long-range strike failing to trouble Rab Douglas after being put through on goal by Mulgrew.
Dundee had their best chance of the first half when former Celtic youth Ryan Conroy raced down the left-hand side and played Steven Milne inside the box and he managed to cut the ball back to Colin Nish, but his strike was blocked by Scott Brown and the rebound was blazed over by John Baird.
Lennon’s side were given a golden opportunity to take the lead as Lassad was brought down in the box by Benedictus, by the penalty from Celtic skipper Brown was saved by Douglas and the rebound from Kris Commons went wide.
Minutes later, Celtic did take the lead just before the half-time whistle as Hooper turned the Dundee defence after receiving the ball from Brown and diverted it beyond the outstretched arms of Douglas and into the back of the net.
Celtic doubled their lead just after half time as Wanyama unleashed an unstoppable long-range strike that curled past Douglas after receiving the ball from Emilio Izaguirre 25 yards from goal.
The home side could have extended their lead as firstly Hooper was called offside when he poked the ball home from close in and when Lassad got his head onto a cross from the right by Adam Matthews, but his effort was deflected for a corner by Douglas.
With just over a quarter of an hour left and his team comfortably winning, Lennon decided to bring on winger Dylan McGeouch for the first time since he suffered a jaw injury during the Hoops' pre-season friendly game against Real Madrid in Philadelphia.
The chances continued to fall to the home side, but neither Hooper nor substitute Tony Watt could find a way past Douglas in order to extend the lead for the Parkhead side and they were made to settle for the two-goal victory.