There's no exact way to make it happen but you can just try starting the guy who had 13 and backing him up with 35 minute dude and hope for the best. I would also try not to blow out the other team or get blown out.
When I one position train I just dress nine players and have the training position play the full 48 in one game. It's not ideal for winning games but it maximizes my training.
Managing minutes in this game is hard and involves a lot of trade offs (i.e. better training for worse game performance). It's an intentional element of the game design and makes it a better game.