Team impact:
2004 Suns- 29 wins, 101.4 O rating, 21st (No nash)
2005 Suns- 62 wins, 114.5 O rating, 1st (with Nash)
Thats a huge transformation with just Nash being the main piece added. In 2004, Marion/Amare/Johnson had a 104.8 O rating when they were on the court together. In 2005, those 3+Nash equaled a 122.2 O rating. Thats how much impact Nash had on the offense.
2012 Suns- 0.29 SRS, 106.2 O rating, 9th (with Nash)
2013 Suns- -5.75 SRS, 101.2 O rating, 29th (no Nash)
The Suns went from a top 10 offense with Nash to almost the worst offense without Nash.
According to NBA.com, From 02-10, Steve Nash's offensive teams were ranked #1 every single year in offensive rating. 9 straight years of #1 offenses
Missed games from 2005-2012:
11-26 record (.297, 24 win pace)
-5.87 SRS (Equivalent to the 2013 Suns SRS)
105.2 O rating vs 106.1 Opp D rating (-0.87 offense

)
So the Suns offense was actually below average in the games Nash missed. For all the talk about Nash's crap defense, the Suns had an astonishing 113.5 D rating in these games. That would be by far the worst in the NBA this year.
Here are the missed game numbers from 2005-2007, Nash's Peak:
4-12 record
-6.45 SRS
104.7 O rating vs 105.7 opp D rating (-0.99 offense)
The Suns allowed a 112.6 D rating in these games. This is peak Nash where the team played like a 60 win team when he was on the court, yet acted like one of the worst teams when he is off.
Best offenses:
Here are the top offenses in NBA history by O rating,
includes playoffsRank Year Team eORtg Offense
1 2007 Phoenix Suns 116 3.25
2 2005 Phoenix Suns 116.1 2.923 1971 Milwaukee Bucks 108.2 2.72
4 2010 Phoenix Suns 116.4 2.595 1982 Denver Nuggets 113.4 2.56
6 2004 Dallas Mavericks 110.8 2.497 1975 Houston Rockets 104.1 2.4
8 1987 Los Angeles Lakers 115.9 2.34
9 2004 Sacramento Kings 110.3 2.33
10 2006 Phoenix Suns 113.1 2.31
11 2009 Phoenix Suns 114.4 2.1312 1988 Boston Celtics 114.7 2.12
13 1998 Seattle Supersonics 113.2 2.07
14 1996 Chicago Bulls 116.3 2.02
15 1985 Los Angeles Lakers 114.6 2.01
16 1978 San Antonio Spurs 106.8 2
17 1995 Seattle Supersonics 116 2
18 2004 Seattle Supersonics 109.3 1.99
19 2002 Dallas Mavericks 110.4 1.9820 1997 Seattle Supersonics 114.4 1.94
7 out the top 20 offenses of all-time belong to a Steve Nash team. No one in history has done anything like that.
The most common criticism of Nash is his playoff offenses, yet his teams played amazing offense in the playoffs.
Best playoff offensive ratings relative to opponents D rating:
1. Suns 2005 16.2
2. Suns 2010 12.63. Lakers 2001 12.2
4. Suns 1992 11.8
5. Suns 1995 11.5
6. Bulls 1991 10.9
7. Lakers 1987 10.5
8. Nuggets 2009 10.2
9. Mavericks 2003 10.010. Lakers 1985 9.8
11. Lakers 1998 9.5
12. Kings 2003 9.5
13. Magic 1996 9.3
14. Rockets 1997 9.3
15. Lakers 1989 9.1
16. Mavericks 2002 9.017. Spurs 2006 9.0
18. Suns 2006 9.019. Bulls 1993 8.9
20. Mavericks 2005 8.7
Here are Nash's playoff on court Offensive rating
05: 118.7
06: 116.5
07: 112.5
10: 120.6

05 vs Grizzlies: 124.1 Ortg vs 102.9 Drtg (+21.2)
05 vs Mavs: 118.1 Ortg vs. 104.1 Drtg (+14)
05 vs Spurs: 115.7 Ortg vs 98.8 Drtg (+16.9)

06 vs Lakers: 115 Ortg vs 105.7 Drtg (+9.3)
06 vs Clippers: 115.1 Ortg vs 103.8 Drtg (+11.3)
06 vs Mavs: 113.3 Ortg vs 105 Drtg (+8.3)
07 vs Lakers: 111.8 Ortg vs 105.6 Drtg (+6.2)
07 vs Spurs: 109.6 Ortg vs 99.9 Drtg (+9.7)
10 vs Blazers: 111.5 Ortg vs. 107.1 Drtg (+4.4)
10 vs Spurs: 124.5 Ortg vs 104.5 Drtg (+20)
10 vs Lakers: 122 Ortg vs 103.7 Drtg (+18.3)
RAPM:
Best offensive RAPM's in the RAPM era:
Year Rank Name Offense per 100
2007 1 Steve Nash 7.92010 2 Dwyane Wade 7.6
2007 3 Baron Davis 7.5
2008 4 Steve Nash 7.42010 5 LeBron James 7.1
2007 6 LeBron James 7.1
2009 7 LeBron James 6.6
2007 8 Manu Ginobili 6.5
2010 9 Steve Nash 6.32007 10 Tim Duncan 6.3
2011 11 Steve Nash 6.2
2009 12 Steve Nash 6.25 out of the top 12 belong to Nash. This doesn't even include his 2005 season where he had a 121.7 On court offensive rating, the highest ever since 1997
System/conventional lineup argument:
There is an argument that somehow Nash can only succeed in 1 system (Dantoni). D'Antoni left after 2008, yet Nash still had 2 of his best offenses in the next 2 years. Here is how D'Antoni's offenses ranked in the years after leaving Nash:
17th
17th
7th
17th
9th
21st
Looks like Nash deserves more of the credit than D'Antoni.
Nash has had success with more conventional lineups. In 2006, He succeeded with Kurt Thomas as his center. In 2008, Nash had a 119.1 O rating with Shaq/Amare on the court. That's a traditional big lineup and Nash was as good as ever.
Here is how certain players did with and without Nash. Nash showed huge impact on these players and it could be argued that Nash made them stars.
Marion:
Before Nash: .513 TS%, 107 O rating
Nash comes to Phx: .566 TS%, 116 O rating
08 w/Nash: .594 TS%, 119 O rating
08 after Nash: .503 TS%, 99 O rating
Amare:
Before Nash: .536 TS%, 102 O rating
Nash comes to Phx: .617 TS%, 121 O rating
with Nash 2010: .615 TS%, 117 O rating
after Nash 2011: .565 TS%, 109 O rating
Shaq:
08 before Nash: .577 TS%, 100 O rating
08 with Nash: .605 TS%, 103 O rating
09 with Nash: .623 TS%, 117 O rating
10 leaves Nash: .565 TS%, 104 O rating