The call to holiness is rooted in baptism.  But the priesthood is seen by the magisterium as much more than that.  Let me cite two representatives of that concept.
In inaugurating the Jubilee Year for Priests at Vespers on Friday, June 19, 2009, Pope Benedict XVI stated in his homily: "The priesthood is the love of the heart of Jesus for the human race.  It was God's plan to make Christ "the heart of the world.  This plan is achieved in history "as Jesus gradually become the HEART of human heats.  It starts with those called to be closest to him: namely his priests.  Citing St. Jean-Baptist Marie Vianney, Pope Benedict states "After God, the priest is everything!...Only in heaven will he fully realize what he is."

At the World Synod of Bishops held in Rome September 30-October 28, 1990, Archbishop Daniel Pilarczyk stated that: "The sacrament of Holy Orders marks the priest as a member of the Christian faithful who has been permanently configured by Christ [alter Christus]