You can start 3 players and it'll be fine. "Lucky fan"s replace the blanks in the lineup, and replace those who foul out also.
I did this today too, for the same reason as you. Training + extra income from 3rd game...but found out after the game that now I'm paying wages this week when I wouldn't have done if I just won the game. It's costing me money instead! So bear that in mind.
My game: http://www.buzzerbeater.com/match/90355665/boxscore.aspx
I dressed 5 players and as you can see 3 fouled out. One of the initial lucky fans actually got injured so a total of 4 played in the game :D