I agree, the unfaithful servant is simply not saved and therefore incapable of serving the master.
"...his commands are not burdensome, for everyone born of God has overcome the world." (1 John 5:3b,4a)
Jesus said, "If anyone loves me, he will obey my teaching...He who does not love me WILL NOT OBEY MY TEACHING." (John 23, 24)
"Those controlled by the sinful nature CANNOT PLEASE GOD. You, however, are controlled not by the sinful nature but by the Spirit, IF THE SPIRIT OF GOD LIVES IN YOU. And if anyone does not have the Spirit of Christ, HE DOES NOT BELONG TO CHRIST." (Romans 8:8,9)
Abraham was circumcised as a requirement of the covenant God made with him. This circumcision, or absence of the flesh, was the outward proof or evidence that Abraham was indeed in covenant with God:
"You are to undergo circumcision, and it will be the SIGN OF THE COVENANT between me and you." (Genesis 17:11)
In the same way today the absence of the flesh (specifically the sinful deeds of the flesh) is the outward proof or evidence that our hearts have been circumcised by the Spirit and that we are in fact in covenant with God through Christ.
"In him you were also circumcised, in the PUTTING OFF OF THE SINFUL NATURE (or flesh), not with a circumcision done by the hands of men but with the circumcision done by Christ..." (Col. 2:11)
"We know that we have come to know him if we obey his commands. The man who says, 'I know him,' but does not do what he commands is a liar, and the truth is not in him. But if anyone obeys his word, God's love is truly made complete in him. This is how we know we are in him: Whoever claims to live in him must walk as Jesus did. "
(1 John 2:3-6)
Love is made complete among us so that we will have confidence on the day of judgement, BECAUSE IN THIS WORLD WE ARE LIKE HIM."
(1 John 4:17)