And just as much of an unknown is what Harvin's role will be when he's finally given the OK to get back in a game for the first time in a calendar year.
The analysis of how Harvin would fit with the Seahawks first started when he was acquired in a trade with Minnesota in March, then was put on hold when Harvin underwent hip surgery to repair an injured labrum in early August.
It's all restarted this week as Harvin returned to practice for the Seahawks, ahead of the initial timeline that was presented for his recovery. Coach Pete Carroll reiterated Thursday that Harvin's return remains a day-to-day evaluation and made no promises about whether his debut would come on Monday night at St. Louis or is still a couple of weeks away.
Harvin was not listed on the Seahawks injury report Thursday since he is not on the active roster.
"It's a day-to-day, almost a drill-to-drill kind of situation to see if we're managing him properly, to bring him back. It would be great to see him play this weekend, but that's not part of what we're counting," Carroll said Thursday.
When he does return, Harvin will join an offense that will always be based around the run first and spreads the ball to its various pass catchers. Headed into Monday's game which will mark the midway point of the season for Seattle no receiver has more than Golden Tate's 27 catches and six players have at least 10 receptions. The Seahawks' leader in touchdown catches is Zach Miller, with three, while Jermaine Kearse is the only other player with more than one TD catch with two of his eight receptions going for touchdowns.
How will Harvin fit in? He thinks it'll be very similar to his first couple of seasons with Minnesota, when he was working under current Seattle offensive coordinator Darrell Bevell.
"It should be a lot similar especially dating back to my first two years when coach Bevell was my offensive coordinator with the Vikings," Harvin said. "I expect it to be a lot similar. I don't expect pretty much anything to change."
Sidney Rice was Harvin's teammate during those two seasons with the Vikings, before signing with the Seahawks before the 2011 season. The best season of Rice's career was 2009, when he caught 83 passes for 1,312 yards and eight touchdowns and often found himself with single coverage because Harvin was on the field.
"Put a package in and let him make plays; that was his role," Rice said. "He mostly played in the slot but he did play on the outside quite a bit depending on what packages we had in for him. I'm sure eventually once he gets healthy we'll start seeing the all-around Percy Harvin, lining up on the outside, on the inside, running back, who knows what's going to come of that."
While Harvin is known for his blazing speed, for much of his career it hasn't been used to try to beat defenses deep downfield. Harvin has caught 280 passes in his career and 210 of those receptions have come either behind the line of scrimmage or within the first 10 yards of the snap, according to STATS Inc. What's made Harvin so successful is his ability to turn those short catches into big plays.
For his career, Harvin is averaging nearly 7 yards after catch, meaning the many quick screens that were thrown his way with the Vikings were turned into meaningful gains. Last season, before being injured against Seattle in Week 9, Harvin was averaging 8.9 yards after catch. That was the best in the NFL for any wide receiver with more than 10 receptions.
"He's a gifted athlete," Bevell said. "He's got great quickness, he can make guys miss. He's got great toughness. He runs like Marshawn (Lynch) once he has the ball. He can run through people, he can run around people. He can make people miss. All those things together help him make those big plays."