Striker pair Daryl Murphy and David McGoldrick netted in the third and sixth minutes to hand the Blues a 2-0 half-time lead against Rotherham United at Portman Road.
Kevin Bru was handed his full home debut and Paul Anderson also returned to the side, with Cole Skuse, who has been suffering with a toe injury, missing out and Teddy Bishop dropping to the bench.
The Millers included ex-Blues keeper Scott Loach and former loanees Frazer Richardson and Paul Green from the start, but on-loan Town pair Paul Taylor and Anthony Wordsworth were ineligible.
Loach was forced into action in only the second minute. David McGoldrick swept a pass wide to Jonny Parr at right-back and the Norwegian sent over a left-footed cross to the far post from where Daryl Murphy smashed a low volley which the Rotherham keeper saved down to his right. The ball was played back into the area and Sammon saw a shot deflect just wide.
From the resultant corner the Blues went in front. Skipper Luke Chambers headed Anderson’s cross goalwards, Loach blocked but Murphy was on hand to nod the loose ball home to claim his fourth goal of the season.
Three minutes later it was 2-0. Luke Hyam brought the ball forward towards the edge of the area and teed up McGoldrick 25 yards out and the striker lashed a strike to Loach’s left and into the net for his third goal of the campaign.
The Blues, looking as confident as they have for some time, immediately went looking for a third and on nine McGoldrick was sent away on the right but chipped into Loach’s hands from a difficult angle.
Rotherham started to make some impact on a game which already looked all but lost. On 11 Anderson blocked Ryan Hall’s edge of the area strike, then five minutes later Alex Revell shot well wide from a similar distance.
One-time Braintree striker Revell had another opportunity on 19 when Joe Skarz’s effort was deflected to him but he missed his kick and Chambers cleared.
But Town were still presenting the greater threat and in the 23rd minute McGoldrick tricked his way to the edge of the area before being dispossessed by Skarz just as he looked set to score his second stunner of the afternoon.
A minute later, Millers’ defender Kari Arnason was booked by replacement referee Kieth Hill for blocking Anderson as he broke on halfway. On 27 Revell nodded a Ben Pringle cross into Gerken’s arms.
Chambers charged down a Hall shot from the edge of the box in the 32nd minute with the ex-Southend man claiming - somewhat hopefully - for handball. The Blues, who up to then had been stroking the ball around confidently but without threatening to add to their lead, made heavy weather of clearing the danger and Pringle was allowed to shoot wide.
Millers’ skipper Lee Frecklington was booked for a foul on Anderson in the 33rd minute before the visitors created their best opening of the half.
Pringle sent in a cross from the left and an unmarked Hall powered a header straight at Gerken from seven yards. The Blues keeper couldn’t hold on to the ball but Tyrone Mings was on hand to clear the danger.
Town weren’t far from making it 3-0 in the 37th minute when Anderson floated a cross to Berra, the Scotland international’s header sending Loach scampering down to his right to scramble the ball past the post. Loach was forced to save again a minute later when Chambers headed goalwards from Anderson’s right-sided corner.
As half-time approached Town twice went close to adding to their lead. First Arnason got in just ahead of McGoldrick to nod Mings’s cross wide at the far post, then, after Bru had returned the cleared corner to him on the right, Anderson skipped past two defenders and into the box but screwed his shot well wide.
In injury time Parr headed over from an Anderson cross from the left, moments before referee Hill blew his whistle to end the half.
Town might well have been more than two goals ahead at the break and that wouldn’t have been an unfair reflection of the half.
The Blues had oozed confidence going forward with McGoldrick showing just why Leicester were so keen to take him into the Premier League before the transfer window closed, adding to his increasingly lengthy list of distance strikes, while Murphy netted a typical predator’s close range effort.
Rotherham’s one real chance was Hall’s header and the Blues had shown the occasional moment of defensive hesitancy. Overall though, McCarthy’s men had been well on top.
Town: Gerken, Parr, Mings, Berra, Chambers (c), Bru, Hyam, Anderson, Murphy, McGoldrick, Sammon. Subs: Bialkowski, Smith, Tabb, Hewitt, Henshall, Bishop, Bajner.
Rotherham: Loach, Skarz, Arnason, Broadfoot, Hall, Frecklington (c). Revell, Bowery, Green, Richardson, Pringle. Subs: Collin, Brindley, Becchio, Swift, Derbyshire, Clarke-Harris, Rowe. Referee: Keith Hill (Hertfordshire).