I played Americans with the black pieces two days in a row and with good results.
Feeling a bit tired after all the workout on the rest day I ate a heavy brunch before the game against Kamsky yesterday. For about three hours I felt good, and he went astray early with Re2, instead of Rf3. I got a comfortable edge with black early on, somewhat similar to the game against Aronian.
In the fourth hour of play I could neither calculate properly nor take decisions and nearly lost my way. Capturing on b2 would ensure a winning rook endgame, but short on time I just moved Be7 without any real purpose. Fortunately my advantage was still significant. I.ve seen the computer recommended a rook endgame rather then the bishop endgame I chose, but this might be a horizon effect. I was pretty optimistic and after his Bc3 I was clearly winning. Nakamura went down against Aronian, and suddenly I was the sole leader with two rounds to go.
Today, against Nakamura I just felt in excellent shape and played quickly and confidently. My initiative and pressure in the f-file was sufficient to compensate for his bishop pair. His decision to force a draw by repetition around move 30 was probably a wise choice.
Aronian-Kamsky was a draw as well, and going into the last round Sunday (starting already at 11 am local time), three players are still in contention for 1st (I.ve got 3.5 points, Nakamura 3, Aronian 2.5).
In the last round I.m white against Aronian and Kamsky white against Nakamura.
Magnus Carlsen, St. Louis, September 14th, 2013