Looks like every single free agent cornerback is better than Blake.
From PFF's rankings:
https://www.profootballfocus.com/blog/2016/01/11/pro-2016-free-agency-tracker/
1. Sean Smith 83.8 CB 29 Chiefs 967 UFA
2. Josh Norman 83.7 CB 28 Panthers 1203 UFA
3. Adam Jones 83.3 CB 32 Bengals 945 UFA
4. Casey Hayward 82.7 CB 26 Packers 1067 UFA
5. Trumaine Johnson 82.2 CB 26 Rams 931 UFA
6. Janoris Jenkins 80.7 CB 27 Rams 1064 UFA
7. Patrick Robinson 79.4 CB 28 Chargers 713 UFA
8. Leon Hall 78.4 CB 31 Bengals 735 UFA
9. Prince Amukamara 78.4 CB 27 Giants 779 UFA
10. Brandon Boykin 76.9 CB 26 Steelers 407 UFA
11. Terence Newman 76.3 CB 37 Vikings 1014 UFA
12. Josh Thomas 75.4 CB 27 Cowboys 67 UFA
13. Shareece Wright 74.7 CB 29 Ravens 502 UFA
14. William Gay 74.5 CB 31 Steelers 1234 UFA
15. Kyle Wilson 74 CB 29 Saints 509 UFA
16. Tavon Wilson 72.7 CB 26 Patriots 83 UFA
17. Jeremy Lane 72 CB 26 Seahawks 356 UFA
18. Nolan Carroll 71.6 CB 29 Eagles 771 UFA
19. Crezdon Butler 70.9 CB 29 Lions 23 UFA
20. Charles Tillman 68.3 CB 35 Panthers 723 UFA
21. Darrin Walls 67.9 CB 28 Jets 125 UFA
22. A.J. Bouye 67.6 CB 25 Texans 209 RFA
23. Cortland Finnegan 67.5 CB 32 Panthers 324 UFA
24. Sterling Moore 66.8 CB 26 Buccaneers 729 UFA
25. Cassius Vaughn 66.4 CB 28 Chargers 44 UFA
26. Darryl Morris 63.4 CB 25 Texans 96 RFA
27. Alan Ball 60.6 CB 31 Bears 255 UFA
28. Brandon Harris 60 CB 26 Titans 0 UFA
29. Brice McCain 58.6 CB 29 Dolphins 735 CUT
30. Tarell Brown 57.2 CB 31 Patriots 163 UFA
31. Phillip Adams 56.6 CB 28 Falcons 435 UFA
32. Corey White 53.9 CB 26 Cardinals 114 UFA
33. Marcus Sherels 53.7 CB 28 Vikings 9 UFA
34. Brynden Trawick 52.4 CB 26 Ravens 88 RFA
35. Tracy Porter 50.5 CB 30 Bears 856 UFA
36. Jerraud Powers 49.5 CB 29 Cardinals 935 UFA
37. Ron Brooks 49.2 CB 27 Bills 54 UFA
38. Will Blackmon 47.2 CB 31 Redskins 882 UFA
39. Jayron Hosley 47 CB 25 Giants 539 UFA
40. Coty Sensabaugh 46.1 CB 27 Titans 1021 UFA
41. Neiko Thorpe 45.5 CB 26 Raiders 464 RFA
42. Josh Robinson 44.8 CB 25 Vikings 12 UFA
43. Tashaun Gipson 44.6 CB 26 Browns 822 UFA
44. Mike Jenkins 44.4 CB 31 Buccaneers 342 UFA
45. Cary Williams 44.1 CB 31 Redskins 645 UFA
46. Trumaine McBride 43.8 CB 30 Giants 345 UFA
47. E.J. Biggers 43.7 CB 29 Eagles 571 UFA
48. Johnson Bademosi 43 CB 26 Browns 176 UFA
49. Jalil Brown 42.8 CB 28 Colts 315 Colts
50. Jamell Fleming 41.5 CB 27 Chiefs 157 UFA
51. Chris Owens 39.6 CB 29 Saints 13 UFA
52. Sherrick McManis 39.1 CB 28 Bears 302 UFA
53. Morris Claiborne 38.5 CB 26 Cowboys 672 UFA
54. Greg Toler 35.9 CB 31 Colts 692 UFA
55. Antwon Blake 35.1 CB 26 Steelers 1046 UFA