With three players out for an extended period with injury, in addition to three players listed as questionable for Wednesday's start against the Nuggets, the Celtics were working with some scanty numbers in practice on Tuesday.
"We needed some of you in practice today," Rivers joked to the group of reporters after the session, which was also missing Nate Robinson due to a family matter.
With six players listed on the injury report, Rivers has been drawing up different starting lineups on a daily basis, a task that has become quite challenging.
"I've never done as much preparation work with strange lineups than I've done over the past week," Rivers said. "I'm just trying to prepare myself and them, just in case. Some of the guys were laughing, but I told them, 'hey guys, this could be our lineup.'"
No matter what roster combination is sent onto the court, it's the Celtics' established core of veterans that has helped maintain the winning mentality in Boston. Rivers noted that the Big Three has definitely stepped up to lead the team while a collection of key players suffer with injury or sickness.
"It's great to have Kevin [Garnett] and Ray [Allen] and Paul [Pierce]," Rivers said. "They were very serious today with the guys that we had."
According to Rivers, Garnett even scolded a few of the younger players who weren't taking their practice time with the starters seriously. That's the kind of leadership that has lifted the Celtics to a seven-game win streak, and to the top of the Eastern Conference.
For team captain Paul Pierce, it doesn't matter how many players end up on the sidelines. At the end of the day, there are no excuses.
"For this group, it doesn't matter who we put on the court – we feel like we're going to win," Pierce said.
That mentality will come in handy this week for the C's, as they play three games over the next four days, starting with Carmelo Anthony and the red-hot Denver Nuggets, who are also riding a seven-game win streak.
"We just gotta be prepared," Pierce said of Wednesday's matchup. "We can't get too comfortable with the win streak … we've got bigger goals right now and it's not just about a seven- or eight-game win streak, but the long run."