Exegesis:

houtōs kai humeis … legete ‘so you also … must say.’ It is also possible to take houtōs kai humeis as independent, ‘so you also,’ i.e. ‘so with you too,’ “it is the same with you” (Good News Translation), but this appears less probable. houtōs kai draws a parallel between the servant of v. 9 and Jesus’ hearers.

panta ta diatachthenta humin ‘all you were told to do.’

douloi achreioi esmen lit. ‘we are useless servants.’ For the various interpretations of achreioi cf. commentaries, especially Plummer, Lagrange. Here it refers to servants who are aware that they have done only what they ought to do, and no more. Hence achreioi is best understood as expressing the servant’s modesty, cf. Grundmann, and New English Bible, “deserve no credit”.

ho ōpheilomen poiēsai pepoiēkamen ‘we have (only) done what we ought to do.’ The perfect tense of pepoiēkamen denotes an act that has been accomplished.

Translation:

Say, i.e. to each other; hence the subsequent pronouns are taken as inclusive, e.g. in Huautla Mazatec.

Unworthy servants, i.e. ‘undeserving servants’ (see Exegesis), ‘servants who do not deserve (or, are not worthy of) praise/thanks/reward/credit.’

Only, or, ‘nothing more than,’ cf. on 4.8.

Quoted with permission from Reiling, J. and Swellengrebel, J.L. A Handbook on the Gospel of Luke. (UBS Handbook Series). New York: UBS, 1971. For this and other handbooks for translators see here . Make sure to also consult the Handbook on the Gospel of Mark for parallel or similar verses.