Welcome to the boards Numbskull.
The number in the "Inj" column on lists of position players indicates each player's susceptibility to injury - specifically, the location of the injury chance roll on his card. It ranges from 0 (cannot be injured) to 6 (most susceptible). Like Stoney said that number won't change.
0 - no injury chance
1 - injury chance on roll of 2 or 12
2 - injury chance on roll of 3 or 11
3 - injury chance on roll of 4 or 10
4 - injury chance on roll of 5 or 9
5 - injury chance on roll of 6 or 8
6 - injury chance on roll of 7
After the inury roll comes up for a player a 20 sided die is rolled to determine how many games he'll miss. A 12 or 13 was rolled for Laureano so he was sidelined for 3 games. You can read all about it
here.