Boyd, a two-time Premiership winner with Rangers, saw his current employers overcome Celtic 2-1 on Sunday.
The Kilmarnock and former Rangers striker, Kris Boyd, has delivered a stinging response to Youssouf Mulumbu after the Celtic midfielder posted on Instagram following the Bhoys' 2-1 defeat at Fir Park on Sunday.
Mulumbu, who left Kilmarnock at the end of his contract in the summer, was making his debut for Celtic at the home of his previous employers.
But the 31-year-old's homecoming was ruined by Stuart Findlay, the former Bhoys defender who scored the winner for Killie in stoppage time.
Mulumbu wrote afterwards: "Not the result we wanted but we win together and lose together thank you to the fans especially @CelticFC supporters proud to wear that shirt for the 1st time and we’ll fix what didn’t work today ..."
And Boyd, who won two Scottish Premiership titles for Celtic's rivals Rangers but was an unused substitute against Brendan Rodgers' side on Sunday, replied: "You play today mate? I was more effective on the bench".
Celtic had led the match courtesy of Leigh Griffiths' 34th-minute opener, but Kilmarnock drew level half an hour later through another ex-Rangers man, Chris Burke.
Burke then turned provider for Findlay, to leave the Bhoys sixth in the standings - a point and four places behind Rangers.