Seth Partnow has a piece up at the Washington Post where he argues that Lebron has entered his physical decline and cites two (damning) pieces of evidence. First that Lebron is getting blocked at the rim at a much higher rate the past two seasons (9.4% of the time this year vs 5.2% his final year in Miami) and his FG% at the rim has declined EVEN when ignoring those blocked shots. I will add in a 3rd piece of evidence, his FT rate is the 2nd lowest of his career, ahead only of his sophomore season, and 5-6 percentage points below his time with Miami. If that is the only evidence available it certainly seems inarguable that Lebron's physical prime is behind him.
There are some encouraging signs in the opposite direction. While Lebron is finishing at the rim at a substantially worse rate, he is getting to the rim better than at any other point in his career. According to Basketball-Reference Lebron has taken 43.5% of his shots inside of 3 ft so far this year, substantially above his 2nd best year of 39.9% and miles better than his career average of 34.3%. He is also taking a few extra shots from between 3 and 10 ft, 13.6% vs career average of 12.2% and his 3pt rate is right around his career average, which means these extra close 2s are all coming at the expense of shots from 10 ft out to the 3 pt line, the easiest shot in the league to take, and the least valuable.
This is not a compositional change either where Lebron is passing out of long 2s and so his percentages from other spots rise as a result of lower usage. James' usg, at 32.9 after last nights game, is the highest it has been since he left Cleveland for Miami and his turnover rate is the 2nd lowest of the past 6 seasons. Meanwhile a couple of other indicators of athletic ability, steal and block percentages, are right at his career average.
So far this season James' decline in efficiency at the rim, combined with his worst 3 pt shooting season and a below average FT% have overwhelmed his large improvement in shot selection (for lack of a better term). Considering that he has finished the last 7 years at 33% or above from 3 and the last 4 years above 35% it is highly unlikely that he has suddenly become Josh Smith bad at 3 pt shooting.
In conclusion Seth Partnow is probably correct that Lebron has entered into his "decline", but his numbers are an exaggeration of that decline without the proper context. Lebron's decline is likely to be gradual, and at times almost imperceptible, which is not at all unprecedented as other NBA greats like Kobe, Duncan, Jordan and (especially) Karl Malone have managed to fight off aging to varying degrees.