Here are some stats for 3-sets matches that began with a bagel (based on WTA maindraw matches 1997-2010):
The most common set scores in the 2nd and 3rd set are 6-4 and 6-3 - but the variation is high, cf. lists below.
An inverse bagel (0-6 6-0 X-X) has only happened twice;
Elena Dementieva
def. Elena Bovina (Gaz de France Stars 2004, Final, I.hard); 0-6 6-0 6-4
Monica Niculescu
def. Ekaterina Ivanova (Tashkent Open 2010, 2nd, Hard); 0-6 6-0 6-1
The majority of bagel-begun-3-setters are close in the 2nd set - 71% of the matches have a score of 6-3(+) in the 2nd set.
...but that number goes down in the 3rd set; 61% of the matches have a score of 6-3(+) in the 2nd set.
Code:
Set scores in 3-sets matches (lww) that began with a bagel; 2nd -- 3rd
SET 2nd
YEAR # __6:0________ __6:1________ __6:2________ __6:3________ __6:4________ __7:5________ __7:6________
1997 14 0.00% (0) 21.4% (3) 7.14% (1) 14.2% (2) 35.7% (5) 7.14% (1) 14.2% (2)
1998 9 0.00% (0) 0.00% (0) 22.2% (2) 33.3% (3) 11.1% (1) 22.2% (2) 11.1% (1)
1999 10 0.00% (0) 10.0% (1) 30.0% (3) 20.0% (2) 20.0% (2) 20.0% (2) 0.00% (0)
2000 9 0.00% (0) 11.1% (1) 0.00% (0) 11.1% (1) 44.4% (4) 22.2% (2) 11.1% (1)
2001 16 0.00% (0) 12.5% (2) 18.7% (3) 31.2% (5) 25.0% (4) 6.25% (1) 6.25% (1)
2002 13 0.00% (0) 7.69% (1) 15.3% (2) 7.69% (1) 30.7% (4) 7.69% (1) 30.7% (4)
2003 15 0.00% (0) 0.00% (0) 13.3% (2) 20.0% (3) 46.6% (7) 0.00% (0) 20.0% (3)
2004 16 6.25% (1) 6.25% (1) 18.7% (3) 25.0% (4) 18.7% (3) 6.25% (1) 18.7% (3)
2005 10 0.00% (0) 20.0% (2) 10.0% (1) 10.0% (1) 10.0% (1) 40.0% (4) 10.0% (1)
2006 11 0.00% (0) 9.09% (1) 0.00% (0) 54.5% (6) 18.1% (2) 9.09% (1) 9.09% (1)
2007 10 0.00% (0) 0.00% (0) 60.0% (6) 0.00% (0) 20.0% (2) 10.0% (1) 10.0% (1)
2008 10 0.00% (0) 30.0% (3) 10.0% (1) 50.0% (5) 0.00% (0) 10.0% (1) 0.00% (0)
2009 11 0.00% (0) 9.09% (1) 9.09% (1) 27.2% (3) 18.1% (2) 0.00% (0) 36.3% (4)
2010 10 10.0% (1) 20.0% (2) 10.0% (1) 0.00% (0) 20.0% (2) 30.0% (3) 10.0% (1)
ALL av (SD) 1.16% (2.9%) 11.2% (8.6%) 16% (14%) 21.7% (16%) 22.7% (12%) 13.6% (11%) 13.4% (9.9%)
Code:
SET 3rd
YEAR # __6:0________ __6:1________ __6:2________ __6:3________ __6:4________ __7:5________ __7:6'x______ __8-6(+)_____
1997 14 0.00% (0) 21.4% (3) 28.5% (4) 7.14% (1) 7.14% (1) 14.2% (2) 14.2% (2) 7.14% (1)
1998 9 0.00% (0) 11.1% (1) 44.4% (4) 11.1% (1) 11.1% (1) 11.1% (1) 11.1% (1) 0.00% (0)
1999 10 0.00% (0) 10.0% (1) 10.0% (1) 50.0% (5) 20.0% (2) 10.0% (1) 0.00% (0) 0.00% (0)
2000 9 0.00% (0) 11.1% (1) 22.2% (2) 11.1% (1) 33.3% (3) 11.1% (1) 0.00% (0) 11.1% (1)
2001 16 0.00% (0) 12.5% (2) 31.2% (5) 31.2% (5) 6.25% (1) 6.25% (1) 6.25% (1) 6.25% (1)
2002 13 15.3% (2) 15.3% (2) 0.00% (0) 0.00% (0) 23.0% (3) 23.0% (3) 23.0% (3) 0.00% (0)
2003 15 0.00% (0) 26.6% (4) 20.0% (3) 13.3% (2) 20.0% (3) 0.00% (0) 6.66% (1) 13.3% (2)
2004 16 0.00% (0) 25.0% (4) 18.7% (3) 18.7% (3) 25.0% (4) 0.00% (0) 12.5% (2) 0.00% (0)
2005 10 10.0% (1) 10.0% (1) 10.0% (1) 30.0% (3) 20.0% (2) 0.00% (0) 20.0% (2) 0.00% (0)
2006 11 0.00% (0) 9.09% (1) 9.09% (1) 45.4% (5) 18.1% (2) 9.09% (1) 0.00% (0) 9.09% (1)
2007 10 0.00% (0) 20.0% (2) 10.0% (1) 40.0% (4) 0.00% (0) 0.00% (0) 30.0% (3) 0.00% (0)
2008 10 10.0% (1) 0.00% (0) 20.0% (2) 10.0% (1) 50.0% (5) 0.00% (0) 10.0% (1) 0.00% (0)
2009 11 9.09% (1) 18.1% (2) 18.1% (2) 9.09% (1) 36.3% (4) 9.09% (1) 0.00% (0) 0.00% (0)
2010 10 20.0% (2) 40.0% (4) 20.0% (2) 10.0% (1) 0.00% (0) 10.0% (1) 0.00% (0) 0.00% (0)
ALL av (SD) 4.6% (6.7%) 16.4% (9.5%) 18.7% (11%) 20.5% (15%) 19.3% (14%) 7.42% (6.6%) 9.56% (9.3%) 3.35% (4.8%)
av = average (aritmethic mean)
SD = standard deviation (pop)