Fowler played just once in the team's past three games due to a quadriceps injury, and he went 0-for-4 in a loss Saturday. Fowler is batting .245 with 13 home runs and 35 RBIs in his first season with the Cardinals.
Siegrist, a reliever, has struck out 25 batters in 27⅓ innings over 31 appearances this season.
Grichuk's return comes after he was demoted all the way to high-A ball in May to work on his approach at the plate.
Grichuk showed how much he has improved by going 2-for-5, including a home run into the third deck at Busch Stadium, in Sunday night's 8-4 win.
St. Louis also demoted outfielder Chad Huffman to Memphis on Sunday.