The world’s No. 1 female tennis star is likely calling it quits for the rest of the season. Serena Williams announced on her website Sunday evening that she is “completely heartbroken and devastated” that she has re-strained her foot and will not be able to compete in the Austrian tournament she had planned as her comeback. Williams was originally injured after stepping on glass at a Munich restaurant. “Keep me in your prayers,” she asked her fans. The unfortunate news means that both Williams sisters are now out of commission; Venus bowed out of the 2010 tennis season last week due to a knee injury.