As the Green Bay Packers look at their return game for 2010, they see both promise and uncertainty, and that goes for both punt and kickoff returns.

On punt returns, it starts with Will Blackmon. There's plenty of promise there, as Blackmon returned three punts for touchdowns during the 2007-08 seasons, but no one can be certain how well he'll come back from the knee injury that ended his 2009 campaign after just four games.

"We're talking about a guy that's coming off major knee surgery, but we also are talking about a guy that's had very good production for us as a returner," special teams coordinator Shawn Slocum said. "Taking that he's healthy, we'll move forward, and I expect him to be a real factor there."

All reports throughout the spring indicated that Blackmon would be ready for the start of training camp. With Blackmon out last year, receiver Jordy Nelson averaged just 5.3 yards on 17 punt returns. Cornerback Tramon Williams nearly doubled that average at 10.4, with the season's longest return of 45 yards, but he only got 13 returns before he was removed from the duty and starting on defense in place of an injured Al Harris.

Overall, the Packers' 6.9-yard average on punt returns ranked just 23rd in the league in 2009. More important, that average was more than 3 yards less than the opponents' average of 10.1. When Blackmon was healthy for all of 2008, he averaged 11.1, good for fourth in the NFC and ninth in the league, while the opponents averaged just 7.5.

The simplest move would be for Blackmon to be back to his old self, helping give the Packers the edge again on punt returns. But until he's back on the field performing in games, any expectations are mere projections.

"Will is a very good punt returner, very shifty," Slocum said. "We'll see once he gets back and he gets totally turned loose if he can make the jump cuts that he's done in the past, which really gave him an advantage returning the ball."

While Blackmon was sitting out organized team activities (OTAs) and the June mini-camp, the Packers looked at a handful of other candidates. Nelson took his share of reps. But Williams was unsigned until the final few days of the offseason program, and it isn't clear how viable an option he is anyway with Harris' return date unknown.

Slocum also tried out a couple of rookie prospects in cornerback Sam Shields and running back Quinn Porter. Shields has electrifying speed but struggled to catch the ball consistently, which will have to change when the pads come on during training camp. Porter was a little smoother catching the ball but, like Shields, has an uphill battle just to land a roster spot.

Slocum noted that it wasn't easy for the young returners in the spring to be going back and forth between catching punts from the right-footed Tim Masthay and the left-footed Chris Bryan, but it's better for everyone if they're tested in that fashion now.

"(Shields) is a dynamic athlete," Slocum said. "He's got difference-making speed, and if you can get the ball in his hand and get him a seam, you have a chance to score touchdowns.

"I think Quinn Porter does a great job of getting lateral and then getting vertical quickly.

"We need to see more consistency in both of them fielding the ball, and a lot of times that's a process you have to go through. We've got a full training camp to go, a bunch of reps for them to continue to get better."

The Packers also would like to improve on kickoff returns, where they ranked 19th a year ago. Nelson was their best option, averaging 25.4 yards on 25 returns, but the team had just one return longer than 28 yards during a three-game midseason stretch that Nelson missed with a knee injury. Nelson also fumbled two kickoff returns down the stretch last season, one on Thanksgiving in Detroit and again in the playoffs in Arizona, though the Packers recovered the latter one.

Blackmon will get a long look for this job as well, but he hasn't been as explosive on kickoffs as he has on punts when healthy. Williams and running back Brandon Jackson also have experience here, while Porter has an intriguing track record, with two 90-plus-yard returns for scores in his final season at Stillman College.

"Each year is a new year," Slocum said. "We've got a number of guys that have ability and have excellent speed. As we go through this process and look at all of them, we'll give them opportunities in those (preseason) ballgames."

Much has been made of the fact that the Packers haven't run a kickoff back for a touchdown since 2000. Blackmon and Nelson have each returned a kickoff all the way over the past two seasons, but both returns were called back by penalties.

It would be nice to end that drought, but more important to Slocum is simply getting decent field position for the offense on a consistent basis. Last year, the Packers' average field position following a kickoff was the 27.3-yard line, ranking a respectable ninth in the league and nearly a full yard better than the league average (26.4).

At a minimum that ranking needs to be maintained, if not enhanced, whether the return unit breaks any long ones or not.

"With the explosiveness of our offense, if we can get the ball outside the 20 or better yet at the 30-yard line, our scoring probability goes way up," Slocum said. "So that's the No. 1 goal, and if we're consistent in getting the ball north and south, then big plays come."