Those two statements are important. You can agree to the first without agreeing to the second (if you believe that El Capitan's "slump" was more than just a slump). You can not agree with the second without agreeing with the first. Let me explain through the power of MATHEMATICS.
The good years (2006-2010)
Both of these quarterbacks started their NFL careers in 2004. Neither got a start in the league until 2006. For Philip Rivers, it was the injury to Drew Brees that opened up the gates for him to become the starter for the San Diego Chargers. For Tony Romo, it was an injury (and poor performance) by Drew Bledsoe that lead to him getting his chance to be the Dallas Cowboys starter. (COUGH)
Both players were almost immediately successful, although Rivers had a much better team around him. Here's how those first five years played out:
Rivers: 1547/2425 (63.8%), 19513 pass yds (8.0 YPA), 135 pass TDs (5.6% TD), 57 INTs (2.4% INT), 137 sacks (5.3% sack)
Romo: 1326/2070 (64.1%), 16650 pass yds (8.0 YPA), 118 pass TDs (5.7% TD), 62 INTs (3.0% INT), 106 sacks (4.9% sack)
For those that are wondering, those last three percentages are the percentage of passes thrown by that player that resulted in that outcome. So, 5.6% of Rivers' throws were for touchdowns. Makes sense? That makes the sack percentage a little different, since a pass wasn't thrown on that play, but I included it to help get a ratio (sacks per pass attempt?) between the two players.
So, what do you see? Well, they're roughly the same player. Romo is a little more accurate, and does a better job avoiding sacks, but throws more picks. Still, they're both very close in every category (Rivers even had 2 rushing TDs to Romo's 3 rushing TDs over this span).
This is going to suck.
Rivers: 704/1109 (63.5%), 8230 pass yds (7.4 YPA), 53 pass TDs (4.8% TD), 35 INTs (3.2% INT), 79 sacks (6.6% sack)
Romo: 771/1170 (65.9%), 9087 pass yds (7.8 YPA), 59 pass TDs (5.0% TD), 29 INT (2.5% INT), 72 sacks (5.8% sack)
It would appear that Romo got even more accurate with his passes, but also a bit more conservative. The yards-per-pass, TD% and INT% are all a testament to that. That would make sense because it appears his offensive line took a dive similar to the Chargers' offensive line.
Rivers, on the other hand, got worse in every single category.
This is probably a good time to mention that Romo is a year and a half older than Philip Rivers. (That collective sigh you hear is every Chargers fan that has been reading up until this point to hear me say something remotely positive about Rivers.)
Catching Up? (2013)
Rivers: 70/100 (70.0%), 798 pass yds (8.0 YPA), 8 pass TDs (8.0% TD), 1 INT (1.0% INT), 5 sacks (4.8% sack)
Romo: 83/115 (72.2%), 771 pass yds (6.7 YPA), , 6 pass TDs (5.2% TD), 1 INT (0.9% INT), 6 sacks (5.0% sack)
Through three games, both guys have taken to their new Offensive Coordinators quite well. Sacks are down, along with turnovers, and completion percentages are high. The YPA and TD% for Romo is surprising if you've never seen a Bill Callahan offense before.
Once again, in good times and in bad, Philip Rivers and Tony Romo are putting up similar numbers and looking very different doing it. Remember that when you're watching Sunday's game and telling someone about how bad of a QB Romo is, that Philip Rivers is almost exactly the same player.