Snell is 0-5 this season with a 5.89 ERA in eight starts and three relief appearances. He has allowed 29 earned runs and 57 hits in 44 1/3 innings, and he has also given up nine home runs.
French, who was recalled from Triple-A Tacoma on June 6, has allowed four earned runs on eight hits in 5 2/3 innings out of the Seattle bullpen. He will make his first start of the season on Monday in St. Louis.
"I like the [pitching] angle that he had," Wakamatsu said. "His delivery is much cleaner that I saw last year. I saw a couple good inside fastballs that he threw, and he worked the changeup around that."
Wakamatsu said Snell took the news of the move well and that Snell believes he can be an asset in the bullpen.
"He's actually talked about feeling like he can help the bullpen better," Wakamatsu said. "I think having experienced it before, and maybe a comfort level in that, he feels like maybe he can do several different things. We'll see how the bullpen goes, but we'll give him an opportunity to be [a long reliever] or, in certain situations, where we might need him for an inning."
The last time Snell was primarily used out of the bullpen was in 2005 with the Pirates. That season, 10 of his 15 appearances were in relief.