Tenshinhan would be a non factor. The only way to change something is for him to
die in this fight. In that case, 1 year later, without Tien, if Yamcha goes first
against Saibaimen and everything goes as we know it, everyone gets killed a lot
sooner, since Tien isn't there to stall by fighting one Saibaiman or by using tri beam.
By the time Goku arrives, everyone is dead. Goku gets killed by Vegeta. Earth is
destroyed. Vegeta goes to Namek and competes against Freeza for the dragonballs.
In the end, neither of the two sides gets his wish. Namek is destroyed and Freeza's
empire continues.