Randy Moss circa 2010 is not the same Randy Moss circa 2007. That said, he still has more than enough value to help a team, especially a team starved for receivers like the St. Louis Rams.
So what is Moss capable of at this stage of his career? Here's Bill Barnwell of Football Outsiders discussing Moss' value in an article at ESPN:
Based on his form in New England and Minnesota, Moss just isn't playing like someone who can dominate at every level. He can still jump over defensive backs and make fantastic catches, but he only has two plays with more than 10 yards after catch, and his success rate -- the percentage of the time he pushes his team towards a new set of downs -- has fallen from 57 percent in 2009 to 46 percent this year.
So, it looks like Moss is going to be best used as a complementary wideout that stretches defenses downfield, like a rich man's Chris Chambers.
That's exactly what the Rams need, a receiver to stretch the field. Prior to the season, that role was reserved for third-year wideout Donnie Avery. Injury felled those plans. Then, GM Billy Devaney swung a deal with the Ravens for Mark Clayton, which turned out to be a huge success for the Rams. Until Clayton was lost for the season in an ugly game at Detroit. Rookie Danario Alexander kind of filled that role in the Rams game against the Chargers, but he was limited because of the time he missed recovering from knee surgery. Now he's recovering from another knee surgery.
Without those guys, the Rams have an very one-dimensional passing game, reliant on short passes and misdirection...making the best of the guys they have at receiver. That worked against Carolina, but might be tougher going against other defenses who can bottle up the Rams.
Moss isn't that #1 WR that he used to be, though with the Rams you could probably expect stats similar to Mark Clayton's. Despite not being the Randy Moss of 2007, he would be an essential role player with the Rams, a prime target for rookie QB Sam Bradford and make the current group of receivers better.