One half of the Washington Redskins’ 2012 campaign is in the books, but the 3-5 team is still waiting to determine what kind of a return it will receive on the investments it made in free agency in the spring.

When the Redskins went shopping then, they sought to add explosiveness on offense by signing wide receivers Pierre Garcon and Josh Morgan and playmakers at both safeties by acquiring Brandon Meriweather and Tanard Jackson.

The team also aimed to upgrade its depth by adding safety Madieu Williams, cornerback Cedric Griffin and inside linebacker Jonathan Goff.

Washington hoped the group would have an impact similar to the one of last season’s free agent class. Nose tackle Barry Cofield and defensive end Stephen Bowen bolstered a defensive front that helped the defense improve from 31st in the league in 2010 to 13th in 2011. Meanwhile, Chris Chester settled in at right guard, starting every game and serving as one of the team’s more consistent linemen.

But most members of this year’s class have had trouble getting, and staying, on the field. And those who have managed to play have provided mixed results.

Garcon was the marquee signing of the year when he agreed to a five-year, $42.5 million contract with $20.5 million of it guaranteed. The former Indianapolis Colt had never been the leading receiver on a team, but the Redskins loved his speed, size and the physical nature with which he played. The belief was that Garcon could come in and team with rookie Robert Griffin III to give Washington a big-play duo for years to come.

The Redskins’ decision-makers appeared to have it right. In the first quarter of Washington’s season opener, Griffin targeted Garcon on four of his team’s first eight offensive plays. The wide receiver caught all four passes, recording 109 receiving yards, including an 88-yard touchdown. But on that touchdown, Garcon ruptured a ligament in the second toe of his right foot. He missed the next two games, tried to play through the injury in two others but wasn’t effective, and has been sidelined ever since.

“Well, obviously, with Pierre, I liked the first quarter [he played],” Coach Mike Shanahan said. “I thought that was great. If he would’ve kept it up, he’d have some great stats, but unfortunately that hasn’t worked out. I’m hoping he comes back. I would like to have him come back this week, but I think it’s probably more conceivable after the bye week, because he’s still so far from being 100 percent.”

Morgan, meanwhile, has played in every game but has yet to make an impact. He has only 23 catches for 263 yards and no touchdowns. But Shanahan isn’t concerned by the slow start. He sees Morgan, who spent the offseason recovering from a leg injury that ended his 2011 season, regaining his confidence, and expects him to begin contributing more.

Morgan agrees.

“I just need to go out there and make plays. That’s basically it,” he said. “I’ve just got to find a way to go out there and overcome whatever it is out there.”

Injury has robbed the Redskins of Meriweather’s services. A two-time Pro Bowl selection with New England in 2009 and 2010, he was expected to fill the void left when Washington allowed oft-injured LaRon Landry to depart via free agency. But Meriweather has yet to set foot on the field. He sprained the MCL and PCL in his left knee in the preseason. He had recovered by the first week of September, but re-injured the knee in practice six days before the season opener. Meriweather aimed to play in Week 4, but hurt the same knee again in a bizarre collision with wide receiver Aldrick Robinson during pregame warmups. He has been sidelined ever since.

Goff tore an ACL in training camp and was lost for the season. Griffin missed three games with hamstring problems.

The Redskins also never got to see what Jackson could do for them, but not because of injuries. The former Tampa Bay Buccaneer, considered the most talented defensive back on the roster, was suspended indefinitely just before the season for violating the league’s substance abuse policy. Jackson would have started opposite Meriweather, Redskins coaches say.

“Obviously, I’m very disappointed in Tanard Jackson. We all know what happened with him,” Shanahan said. “And Meriweather, he had a freak injury the Monday before the first game. . . . You can’t do anything about injuries, but that’s why you get depth.”

Williams was one of those depth signings, but he has started every game at free safety. The former Maryland star has had his ups and downs. Like every other member of the secondary, he has given up big pass plays throughout the season — most recently a 77-yard game-clinching touchdown by New York’s Victor Cruz. But Williams does lead the team with 58 tackles, and three weeks ago returned an interception for a touchdown.

Shanahan isn’t ready to pass judgment on this year’s class, but he believes the second half of the season could bring contributions from some of those players.

“Pierre Garcon is a number one receiver, and you could see that in the first quarter of the New Orleans game,” he said. “. . . I’m obviously disappointed with losing a couple safeties. You have to play with that, but I felt that Madieu has come in and played at a competent level, so I feel good about that.

“Cedric just has to stay healthy, and when he’s healthy, he’s very physical and can help us there. [Morgan] is just coming into his own and healing up and getting some playing time now. He’s got a chance to have an excellent half of the season.”