One way to see whether Mark really presents Jesus as a servant, is to look at articles which assert this, based on the contents of Mark's Gospel. If these articles do not show evidence that the author of Mark presents Jesus as a servant, and not just incidentally, then it may be that this gospel is said to present Jesus as "the Servant" for reasons outside the gospel itself.
Bill Bratt ('Jesus Is a Servant') says that the gospels describe Jesus as a servant, although without drawing a parallel to the Servant of Isaiah 53. Of course, his paper draws on sources other than Mark's Gospel and, to this extent, can reach a valid conclusion that the gospels present Jesus as a Servant. It is well known that both Matthew and Luke contain apparent echoes from Isaiah chapter 53, with its 'Suffering Servant Song', but much of Bratt's paper draws on Mark's Gospel to reach his conclusion. Bratt lists 12 passages from Mark in support of the thesis that this gospel presents Jesus as a servant. Surprisingly, only one (Mark 10:45) of these references provides any actual support for Jesus as a servant, while the remainder appear to be eisegesis:
Mark 10:45 (NAB): For the Son of Man did not come to be served but to serve and to give his life as a ransom for many.
When I look at another site (Christian Apologetics and Research Ministry: An Introduction to the Gospel of Mark) that focusses more generally on Mark's Gospel, without a theme of demonstrating that this gospel portrays Jesus as a servant, this provides the same servant passage, but asserts that this actually portrays Jesus as "the Suffering Servant" :
Mark portrays Jesus as the suffering servant most likely in fulfillment of the servant passages in Isaiah specifically Isaiah 52:13-53:12. The key theme verse in Mark is found in 10:45 which says, "For even the Son of Man did not come to be served, but to serve, and to give His life a ransom for many."
More generally, the absence in Mark of details such as Jesus' genealogy is not evidence that Jesus is portrayed as a servant, as most of the scriptures talk of persons who are clearly not slaves, and without including genealogies.
Rhoads, Dewey and Michie, in Mark as Story, examine Mark's Gospel in considerable detail, with an entire chapter on the characterisation of Jesus, but do not conclude that Mark portrays Jesus as servant. I draw the same conclusion - there is insufficient evidence that a reading of Mark's Gospel portrays him as the Servant of Isaiah chapter 53. The gospel is apparently seen by some as making this distinction because it is a distinction made by Paul and, more obliquely, in the Gospels of Matthew and Luke, so therefore it must be a distinction present in Mark.