in real life they try to avoid matchups during the frist two rounds that occured during the season or matchups that occured during the previous year's tourney.
But in HD, like RL these are used more as guidelines and not always avoided.
If you remember this year's NCAA tourney actually had a couple matchups of BigEast teams (UConn/Cincinnati and Marquette/Syracuse) in the second round.
A few seasons back I played 5 NT games and 4 of them were repeat opponents I had played during the season.