Stellar putting made a big difference for Matsuyama on the last day of the golf major.
The 2021 Japanese champion had his second even-par round of the tournament, improving on a 5-over 77 in the third round.
Matsuyama needs a record-breaking performance over the final 18 holes to retain the green jacket.
World No. 1 Scottie Scheffler leads the field with an 8-under 136 at the midway point.