The 23-year-old outfielder was hitting just .184 with a .276 on-base percentage and one home run through his first 25 games. He was riding a five-game hitting streak but hadn't picked up his batting average since April 7.
"You have to produce at this level," Snider said. "My bat has been getting going lately, but you have to produce consistently."
Anthopoulos believes Snider has been far out in front of pitches, flying open and not producing the kind of swing that allowed him to jump through the Minor Leagues and be projected as a future impact slugger in the big leagues.
"He's pulling off the ball a lot, he's really out front of a lot of balls, he hooks a lot of balls and comes around it, and we need to try to get him to shorten up again and get back to what made him a successful, very good offensive player for us," Anthopoulos said.
"When you try to make those mechanical changes, we tried to make them up here, and he continues to work on them. But you also have to be responsible to try to win as many games as we can."
Anthopoulos said there's no timetable for Snider's return to the big leagues; it depends on when he's able to find his stroke again.
Also on Thursday, the Blue Jays outrighted infielder Chris Woodward in order to activate outfielder Rajai Davis (wrist, ankle) from the disabled list.
Cooper, Anthopoulos said, will be used mostly as a designated hitter, with Adam Lind remaining at first base and Juan Rivera playing his fair share of left field. The GM said he chose to call up Cooper because he "was the one that really had the best approach, and we thought that it was going to translate the best from an offensive standpoint up here."
Snider, the Blue Jays' No. 14 overall Draft pick in 2006, got off to a slow start last year, but Anthopoulos recalls feeling he was close and that he could break out soon. He believes Snider's talent would've allowed him to muster some hits, but fixes need to be made for sustained production.
"He's certainly talented enough, and with his makeup and work ethic, he can play through anything," Anthopoulos said. "But I think ultimately, we don't see Travis Snider as a 7-, 8-, 9-hole bat. We think he has a chance to be a middle-of-the-order bat. But we need to get him right."
Snider has been optioned three times in four seasons, and has accumulated a .246 batting average, .313 on-base percentage and 26 homers through 208 games in the big leagues. Anthopoulos was told by manager John Farrell that Snider handled his demotion like "a total pro" and expressed confidence that he'd be the player the Blue Jays once projected.
"The last thing we need is for Travis to underachieve in his career," Anthopoulos said. "He has the ability to be a great player. We need to do everything that we can to get him there."