Many of the Ravens' regulars started filtering out of the locker room and onto the field about two hours before the start of their preseason opener last week against the Carolina Panthers. Wearing T-shirts and shorts, veterans like Joe Flacco, Justin Forsett and Benjamin Watson walked briefly around the new grass surface at M&T Bank Stadium before settling down on the bench to watch teammates warm up.The scene was similar at NFL stadiums throughout the country last week. First-year New York Giants head coach Ben McAdoo held out starting quarterback Eli Manning and star wide receiver Odell Beckham Jr. Pittsburgh Steelers head coach Mike Tomlin sat down quarterback Ben Roethlisberger and wide receiver Antonio Brown. Quarterback Tony Romo didn't play a down for the Dallas Cowboys, nor did Aaron Rodgers for the Green Bay Packers, or Andrew Luck for the Indianapolis Colts."I think if you took a real hard look at it, you'd probably see that [guys] play less now than they did six, seven or eight years ago," Ravens coach John Harbaugh said this week when asked about players being held out of preseason games. "That's probably the trend you're referring to around the league. That's probably true here, too."During his tenure in Baltimore, Harbaugh has traditionally played his starters one or two series in the preseason opener, about a half in the second game and as much as three quarters in the third, which he's treated as the final dress rehearsal for the regular season. He has rested most of his starters for the fourth and final preseason game.But last week, the Ravens didn't have 20 of their 90 players in uniform for their opener, and at least seven who didn't play weren't dealing with an injury. Harbaugh remained noncommittal this week when discussing who will and won't play Saturday against the Colts at Lucas Oil Stadium, but all indications are that Flacco, who had surgery on his left knee eight months ago but hasn't missed a single rep in training camp, will be held out for one more week."Well, you have to assess, 'Does one series or two series really make a difference?' Because that is all you are playing in the first two preseason games," Flacco said. "If you don't really think it does, you probably decide to do what they are doing."It's a fine line that Harbaugh and other NFL coaches walk in the preseason. The ultimate goal is to have players fresh and healthy heading into the regular season. There are few things more frustrating for an organization than watching a key player go down in an otherwise meaningless game played before swaths of empty seats.However, veterans need game action, too. They need to knock off the rust, develop chemistry with their respective units and make sure they're in game shape. Even Ravens veteran pass rusher Terrell Suggs, who returned to practice this week but won't play Saturday, acknowledged Thursday that there's no substitute for game action."You can't tell in practice. You run around and guys are in shorts and helmets today. The next day they are in shoulder pads. The next day they are back in helmets and shorts. How do you evaluate a guy like that?" said former NFL head coach Herm Edwards, now an ESPN analyst. "That's why preseason games, to me, are more valuable now than ever because the ways the practices are scheduled and what you can do and what you can't do. I understand you're trying to protect the players. You should protect the players, but you still have to evaluate young players and you have to develop young players."Edwards, who coached the New York Jets for five seasons and the Kansas City Chiefs for three, understands why coaches err on the side of caution."You don't want to say it, but … there are only so many hits these guys can take," he said.Still, he feels that the collective bargaining agreement, which limits practice time and the amount of contact allowed in workouts, has altered the decision-making process. Coaches are more apt to rely on young players because it's the only opportunity to evaluate them in game-like situations.Harbaugh, who has been critical of some of the rules governing practice time, maintained that evaluating young players is a "big part" of the organization's preseason focus."You want to see the young guys play in game situations when the tackling is live," he said. "We practice really well, and we see a lot from our guys in practice. The game is a confirmation, of sometimes, guys that don't practice as well, but play well in games. Sometimes guys practice great and don't show up in games. That's something you really need to know."Harbaugh said "everything factors in" to the decision of whom to play in the preseason. That includes things like field conditions, opponent, health of the player, health of the specific position group and how much the coaching staff feels it needs to evaluate certain players.The Ravens held out veteran wide receivers Kamar Aiken and Mike Wallace last week, partly because they wanted to evaluate younger receivers like Jeremy Butler and Keenan Reynolds. Watson sat while young tight ends Maxx Williams, Darren Waller and Nick Boyle logged a ton of snaps."There is always a risk-reward in football. The reward for the player, for me especially, is being in a new place, getting used to game-type situations, doing stuff under game pressure and getting the calls and stuff like that," Watson said. "On the other side, football is a contact sport. It is a game where people get injured, sometimes for the length of an entire year. You always have to weigh that as a coach of the organization and understand that there is an inherent risk when you put guys out there, but you also want to get the team ready for the season."Not only did the Steelers' Tomlin hold several of his offensive standouts out of the preseason opener, he also didn't play Roethlisberger, Brown and running backs Le'Veon Bell and DeAngelo Williams in the second preseason game either.The Giants' Manning had traditionally played a little in the first preseason game under longtime head coach Tom Coughlin, but McAdoo altered that script last week. Manning told reporters this week that sitting out the first preseason game was "not something I ideally like."Colts owner Jim Irsay cited Buffalo Bills' head coach Rex Ryan's aggressive defensive play-calling as the reason Luck didn't play last week. Luck will be plenty rested for the Ravens this week.Harbaugh, meanwhile, has never hid his desire to win in the preseason. The Ravens are 21-12 under him in the exhibition season with wins in 20 of their past 29 preseason games. After beating the Panthers last week, Harbaugh started his post-game news conference by saying, "It's always good to win."Harbaugh and many other NFL coaches have seemingly decided it's even better to keep their top players healthy in the preseason.jeff.zrebiec@baltsun.comtwitter.com/jeffzrebiecsun