Total Skill Index
The Total Skill Index (or TSI) is an official measure of a player's abilities. The formula used for the calculation is unknown, but several somewhat successful attempts have been made in approximating the true function. It is rumoured that HT-Bjorn proclaimed he'll change the TSI calculation formula as soon as someone figures it out.
A common theory is that both form and stamina have a multiplying effect on the TSI, whereas the other skills (for keepers, goaltending only) contribute as a sum of exponential functions.