Randy Moss will run, jump, and catch footballs later today, and he’ll be doing it while Jim Harbaugh is on the other end, throwing spirals and judging his potential future receiver from the vantage point of a quarterback. That’s a role Harbaugh played not too long ago, before he was the head coach at Stanford and the man charged with tutoring Andrew Luck, and before he turned around the lackluster 49ers in just one season while being named the NFL’s best coach in 2011.

The critical, judgmental eye he’s developed in all of those roles will clearly be key today, but another skill will likely be vital too. A poker face.

A week ago Moss reportedly dazzled and amazed during his workout in New Orleans, an outcome that we still greeted with the proper amount of cynicism. He didn’t run the 40-yard dash, and we’d assume/hope that a receiver who’s played football his whole life and professionally for 13 years knows how to run effective routes. Moss showing up to his Saints workout in sound physical condition was another safe and hopeful assumption since he’s been out of football for a year. Finding the local gym is step No. 1 in the instruction manual for NFL comebacks.

Even though the Saints were no doubt aware of those disclaimers, they were still in awe of Moss, the same receiver who caught just 16 passes in 2010 during stops with three teams. That infatuation partly stemmed from the forthcoming exodus at wide receiver for New Orleans, with Marques Colston and Robert Meachem set to be Saints for about 28 more hours.

So if free agency was the catalyst in The Big Easy for the raving about Moss, then Harbaugh could be grimacing while trying to contain his smile in the Bay Area.

The 49ers have roughly $21.8 million to work with against the cap, and they’re about to experience their own mass exit and draining of the wide receiver depth chart. Braylon Edwards was cut in late December after being generally useless, and Ted Ginn Jr. and Josh Morgan are both UFAs, while young Brett Swain is an RFA.

Communication remains open with Ginn and Morgan, and Ginn holds value as a return specialist. But if we entertain the thought of both UFAs leaving, then a passing game that averaged only 183.1 yards per game in 2011 (29th) would be left with only Michael Crabtree, Kyle Williams, and Swain at wideout. Harbaugh could need Moss far more than Moss needs Harbaugh.

The 49ers’ offense that runs first, second, and thinks about passing as a ninth option (San Fran averaged just 28.2 pass attempts per game this year, 31st) is ideal for Moss since he wouldn’t shoulder a major load, and he’d then be utilized as a home run threat, if he does indeed still have home run speed. Physically he’ll be on the field, but his legs and body will be saved while Frank Gore and Kendall Hunter take the bulk of the pounding.

Schematically, it all sounds perfect, and it’s the ideal situation for both Moss and the 49ers, with little risk and a high reward. But that risk will only be minimal if San Francisco doesn’t lose leverage when their other receivers walk, and Moss realizes there’s a sense of desperation.