Lake, 24, had been in the majors since debuting last season after the All-Star break. He hit .284 with a .332 on-base percentage and an OPS of .760 in 64 games in 2013. He burst on the scene as a dynamic player displaying both power as well as the ability to bunt for a hit.
But he regressed this year, hitting only .216 at the time of his demotion with a strikeout percentage of 33.5. He had 102 strikeouts and just 10 walks in 305 plate appearances. Lake began the season in a platoon role playing mostly against left-handed pitching. Eventually he lost playing time to hot-hitting left fielder Chris Coghlan and was reduced to a bench role.
Straily, 25, was acquired on July 4 along with minor leaguers Addison Russell, Bill McKinney and a player to be named later from the Oakland Athletics for Jeff Samardzija and Jason Hammel. Straily was 3-3 with a 3.00 ERA in seven starts for Iowa this year. He's 13-11 with a 4.11 ERA in 41 starts in the big leagues over three seasons, all with the Athletics.
Straily is scheduled to start on Saturday night against the New York Mets but is expected to return to Triple-A Iowa after the game.