Some variation in the handwriting is always expected.
The following signature is from the first page of the contract: http://i.imgur.com/SouZWJz.jpg
I believe that the style is the same, especially his first name "Eric" is very consistent, along with the style of his "e" and "a". I would worry if I found any differences there, the a's tend to stay the same style for all your life since elementary school...
And the speed of the signature is consistent in all three.

Although I don't have the skills of a forensics document examiner, I am very good at telling someone's handwriting since I used to pay a lot of attention to minute details to decode my classmates' absolutely illegible class notes... to the point that I had to decode letter by letter, by comparing and analyzing every curve, slant and direction of their lines. So now I have an eye for these type of things, I can even read a doctor's handwriting