What's actually bologna is your response. No one said you have to be 6'5" 240 to be a "match-up problem." However, there are different types of "match-up problems" and one with his size, speed, and wingspan is and has been a nightmare for opposing defenses. And that player doesn't have to be moved around in order to create favorable match-up issues for the offense. I've seen Calvin Johnson triple covered in games, but I've never seen that of Holt or Harrison. Which might explain why you believe that Harrison and Holt got open more often (not to mentioned the quality of QB throwing to these guys), huh?
Holt and Harrison didn't have to be moved around either to create favorable match-ups. As for them being double covered or triple covered, you're mistaken if you think they never had saw extra coverage.
Were they triple covered? I have no idea. But I highly doubt NFL DCs were content with letting them do whatever they wanted.
From 1999 to 2002, Marvin Harrison averaged 117 catches, 1580 yards, and 13 TDs per year. The next best receivers/TEs on those offenses were...
1999
Terrence Wilkins WR - 565 yards and 4 TDs
Ken Dilger TE - 479 yards and 2 TDs
Marcus Pollard TE - 374 yards and 4 TDs
2000
Jerome Pathon WR - 646 yards and 3 TDs
Terrence Wilkins WR - 569 yards and 3 TDs
Ken Dilger TE - 538 yards and 3 TDs
2001
Marcus Pollard TE - 739 yards and 8 TDs
Reggie Wayne WR - 345 yards and 0 TD
Ken Dilger TE - 343 yards and 1 TD
2002
Reggie Wayne WR - 716 yards and 4 TDs
Marcus Pollard TE - 478 yards and 6 TDs
Qadry Ismail WR - 463 yards and 3 TDs
So Marvin Harrison was at his absolute best in terms of production when he didn't have a top tier secondary target producing. But wait...how? I thought having a great #2 WR caused the #1 WR to get better opportunities and not double covered and thus be more productive?
And I'm sure NFL DCs never thought about rolling coverage towards Marvin Harrison when Jerome Pathon was their #2 WR...and yet he still produced at a ridiculously high level.
Nah. Holt and Harrison got open more often because they were incredible route runners with elite movement skills that knew how to attack and beat the man they lined up against on a play by play basis.
Calvin Johnson is undoubtedly an elite WR. He's undoubtedly a HOFer. He's undoubtedly a match-up problem. But he cannot separate with his routes in the way that guys like Harrison and Holt did. He can't run every route at a high level like Holt and Harrison did. Johnson can do amazing things but I don't know why people always ignore substance for flash. Yes, Calvin will make some amazing plays on jump balls...but at the end of the game, it doesn't matter how you win as long as you are winning. By that I mean, it doesn't matter if you win with route running or jump ball dominance...at the end of the game, 7 catches for 120 yards and a TD is 7 catches for 120 yards and a TD no matter how you did it.
And to finally address your point on triple coverage, might teams have chosen not to triple cover guys like Holt and Harrison because it wasn't a good way to defend them? With a guy like Johnson who is a major deep and jump ball threat, it makes sense to throw more bodies at him. But putting three guys on a player that is an amazing route runner doesn't make much sense. It's wasting defenders because having more bodies on a guy isn't going to stop him from running an incredible route. Which begs the question...if Harrison and Holt were that good in their primes, did teams not just choose to defend them in other ways they saw as more effective?
How many guys were covering Holt and Harrison though? Megatron routinely has 2 and 3 man coverages rolled his way and comes up with a reception unlike anyone in the NFL can. Past or present imo.
Using that, he didn't have another WR rolling away coverage more, opening him up for cleaner receptions.
No, he doesn't.
And as I just pointed out to Memphis, have you considered that teams roll coverage over the top of Johnson because that is an effective way of defending his skill-set? Do you think simply rolling coverage over the top of an elite route runner is an effective way of defending their skill-set?
He also didn't have another WR eating into his targets. As I just pointed out, Marvin Harrison was more productive without a legitimate top tier #2 than he was with one. When you're that good, you're going to do damage if you get enough looks. Another mouth to feed in the offense takes away looks.
To make an analogy to another sport, look at Kevin Love's production with the Timberwolves and with the Cavaliers. On the Cavaliers, he has a lot more talent around him and less defensive attention. Yet, he's scoring almost 10 less points per game.