Ottawa 5-2 could very likely finish 6-2 if Western rest starters so it that case, coupled with a McMaster win, we could see 3 teams tied at 6-2. I think that still gives McMaster #2 seed as they beat Guelph and Ottawa.
If Ottawa went 6-2 by beating Western, they still would end up in fourth place. So maybe Ottawa should rest starters with an eye toward the playoffs.