The Los Angeles Rams do not play starters in preseason games. Many of their key backups don't, either. So the team uses joint practices and scrimmages as a proxy for the missed reps. In these scripted and controlled encounters, the non-preseason participants can play contact football at a higher level than is possible against teammates in practice.
The team emerged with impressive results from the first joint scrimmage with the Dallas Cowboys prior to their preseason opener. But the second such scrimmage with the Los Angeles Chargers was cancelled due to player injuries on the other LA team.