Many Protestant apologists who themselves oppose baptismal regeneration will admit that the Patristics were unanimous in affirming such (e.g., William Webster). To see just a sampling of such vis-a-vis the interpretation of John 3:3-5, see:
Baptismal Salvation, and the New Testament: John 3:1-7
Interestingly, Timothy Kauffman, a Reformed Baptist, has (pathetically, to be honest) tried to refute the claim that Justin Martyr, Tertullian, and other early Chrisitan writers affirmed such. David Waltz has written some good refutations of Kauffman's lame attempts to refute, from the patristics, baptismal regeneration:
Baptismal regeneration and the early Church Fathers: Introduction and Justin Martyr
Baptismal regeneration and the early Church Fathers: Tertullian
Tertullian and the 'baptism of blood'
Timothy Kauffman on baptismal regeneration and the early Church Fathers: my critical examination continues
Baptismal Salvation, and the New Testament: John 3:1-7
Interestingly, Timothy Kauffman, a Reformed Baptist, has (pathetically, to be honest) tried to refute the claim that Justin Martyr, Tertullian, and other early Chrisitan writers affirmed such. David Waltz has written some good refutations of Kauffman's lame attempts to refute, from the patristics, baptismal regeneration:
Baptismal regeneration and the early Church Fathers: Introduction and Justin Martyr
Baptismal regeneration and the early Church Fathers: Tertullian
Tertullian and the 'baptism of blood'
Timothy Kauffman on baptismal regeneration and the early Church Fathers: my critical examination continues