Welker, who is entering his second season with the Denver Broncos, suffered a concussion during Saturday night's preseason game against the Houston Texans. Last season, Welker sustained concussions in Weeks 11 and 14.
"It's tough to see that happen and to a guy like Wes [Welker] who is one of my best friends," Brady said in his weekly interview on Boston sports radio station WEEI. "He is as tough as they come so you hate to see him go through those things, but to see it happen for the third time in a little less than a year is a tough thing."
Welker played six seasons with the Patriots before joining the Broncos in 2013. He had 778 receiving yards and 10 touchdowns last season for Denver. He missed the final three games of the regular season recovering from a concussion, but returned for the playoffs.
Denver opens the regular season Sept. 7 against the Indianapolis Colts.
- Paul Palladino