In the 2009 nba season, LeBron lead a career high +15 on court net rating with Mo Williams as his 2nd best player. He then averaged 7 more points per game in the playoffs while increasing his efficiency, and lowering turnovers
To me, this is LeBron’s most impactful single season of his career, end to end. The cavs won 66 games, and LeBron’s on court +15 net rating was the highest of his career, which includes seasons with Wade + Bosh, and Kyrie + Love. The Cavs had some strong role players like Varejao, Ben Wallace, Delonte, but no real top 20 type players. LeBron’s on-off that year was also a career high +21
For some context on how high a +15 net rating is, here’s the some superstar seasons since 1997 who have crossed: +15 net (only started being recorded since 1997):
2005 Duncan, +17. Notable teammates include Manu, Tony Parker, Robert Horry
2015-2017 Steph, +17, +18, +17. Notable teammates include Draymond, KD, Klay, Iguodala
2025⁄2026 Shai, +17, +18.3. Notable teammates include Chet, J-dub then role players like I-hart, Caruso, Cason Wallace
2020 Giannis, +16. Notable teammates include Middleton, Lopez, and role players like George Hill, Bledsoe, DDV
1998 Shaq, +16. Notable teammates include Eddie Jones, Nick Van Excel, Kobe Bryant, Robert Horry
2008 KG: +16.5. Notable teammates include Paul Pierce, Ray Allen, Rondo, Tony Allen.
Here are some players who have never hit the +15 mark in a regular season:
Jokic, Kobe, Dirk, Harden, CP3, Nash, Tatum
To go deeper into how much impact LeBron had on those Cavs, RAPM is a well known statistical approach that attempts to go beyond on just court and on/off net rating by adjusting for what teammates you play with, and the strength of lineups you faced. LeBron’s 3-year 2009-2011 stretch is the 2nd highest stretch since 1997. His 5-year 2007-2011 stretch is the highest since 1997. https://www.nbarapm.com/player/LeBron_James
In the playoffs across 3 series, LeBron then averaged an absolutely mind boggling 47.5 pts/100 on +10 efficiency adjusting for opponent defense, which is the highest playoff scoring rate of all time within a minimum of 3 series played. This included a 38, 8, 8 series against the number 1 defense Orlando Magic, where the Cavs posted a monstrous +10 offense when LeBron was on court, but also got cooked by a Magic team somehow shooting 41% from 3 and Dwight cooking Varejao/Ilgauskas