I didn't watch the match live, but for those interested here's a video of the match. The illegal move occurred just after the 4:25:35 mark.
Here's the original position (before the 61 has been played and before the 53 was rolled):

              
 
              
 | | White is Player 1
score: 16 pip: 79 | 17 point match Crawford | pip: 180 score: 15
Blue is Player 2 | |
XGID=-CbEDbaa--B--a---aabbb---A:0:0:-1:61:16:15:1:17:10 |
Blue to play 61 |
1. | Rollout1 | 19/13 8/7 | eq: +1.029 |
| Player: Opponent: | 75.54% (G:25.89% B:2.94%) 24.46% (G:15.04% B:1.06%) | Conf.: ± 0.024 (+1.004...+1.053) - [100.0%] Duration: 2 minutes 31 seconds |
|
2. | Rollout1 | 20/14 8/7 | eq: +0.941 (-0.088) |
| Player: Opponent: | 73.31% (G:23.72% B:2.67%) 26.69% (G:17.22% B:2.11%) | Conf.: ± 0.025 (+0.915...+0.966) - [0.0%] Duration: 2 minutes 29 seconds |
|
3. | Rollout1 | 18/12 8/7 | eq: +0.925 (-0.104) |
| Player: Opponent: | 73.02% (G:23.20% B:1.59%) 26.98% (G:17.42% B:1.57%) | Conf.: ± 0.027 (+0.898...+0.951) - [0.0%] Duration: 2 minutes 21 seconds |
|
4. | Rollout1 | 12/6 8/7 | eq: +0.890 (-0.138) |
| Player: Opponent: | 70.88% (G:23.63% B:1.98%) 29.12% (G:18.24% B:1.83%) | Conf.: ± 0.027 (+0.863...+0.917) - [0.0%] Duration: 2 minutes 14 seconds |
|
5. | 3-ply | 19/13 7/6 | eq: +0.726 (-0.303) |
| Player: Opponent: | 67.88% (G:18.41% B:0.80%) 32.12% (G:18.58% B:0.59%) | |
|
|
1 324 Games rolled with Variance Reduction. Dice Seed: 28077514 Moves: 3-ply, cube decisions: XG Roller
|
eXtreme Gammon Version: 2.19.211.pre-release, MET: Kazaross XG2
Knowing his opponent's next roll (a 53) Ed could consider 20/14 8/7, but an XG rollout still likes his actual play (19/13 8/7). According to the rollout, Ed is +0.901 after 19/13 8/7, but only +0.861 after 20/14 8/7. Both moves give him 28 shots at the 8-point blot. After 20/14 8/7 only 53, 52, 32, and 21 miss. After 19/13 8/7 only 63, 62, 61, and 21 miss. In addition 19/13 8/7 keeps the 20 point.
After 19/13 8/7:

              
 
              
 | | White is Player 2
score: 15 pip: 173 | 17 point match Crawford | pip: 79 score: 16
Blue is Player 1 | |
XGID=-CbEDb-a--B-aa----bbbb---A:0:0:1:53:16:15:1:17:10 |
Blue to play 53 |
1. | Rollout1 | Bar/17 | eq: -0.901 |
| Player: Opponent: | 27.58% (G:17.99% B:2.25%) 72.42% (G:22.62% B:2.26%) | Conf.: ± 0.011 (-0.912...-0.890) Duration: 9 minutes 30 seconds |
|
|
1 1296 Games rolled with Variance Reduction. Dice Seed: 28077514 Moves: 3-ply, cube decisions: XG Roller
|
eXtreme Gammon Version: 2.19.211.pre-release, MET: Kazaross XG2
After 20/14 8/7:

              
 
              
 | | White is Player 2
score: 15 pip: 173 | 17 point match Crawford | pip: 79 score: 16
Blue is Player 1 | |
XGID=-CbEDaaa--Ba-a----bbbb---A:0:0:1:53:16:15:1:17:10 |
Blue to play 53 |
1. | Rollout1 | Bar/17 | eq: -0.861 |
| Player: Opponent: | 29.62% (G:19.71% B:2.18%) 70.38% (G:22.66% B:1.82%) | Conf.: ± 0.013 (-0.874...-0.848) - [99.9%] Duration: 9 minutes 24 seconds |
|
2. | Rollout1 | Bar/22 10/5* | eq: -0.894 (-0.033) |
| Player: Opponent: | 29.56% (G:20.64% B:3.21%) 70.44% (G:24.26% B:2.69%) | Conf.: ± 0.015 (-0.909...-0.879) - [0.1%] Duration: 10 minutes 12 seconds |
|
|
1 1296 Games rolled with Variance Reduction. Dice Seed: 28077514 Moves: 3-ply, cube decisions: XG Roller
|
eXtreme Gammon Version: 2.19.211.pre-release, MET: Kazaross XG2