THEME:   MEMO found in phrases [pity this clever theme is part of a tradition of cleverness-shorn Monday offerings]   
GOOD ONES:   Office communication {and theme}   INTERNALMEMO [clever in that MEMO is internal to the phrases]      
BTW:   Scat legend Fitzgerald   ELLA [as SCAT can be scatological, I should think a better clue can be found for the great singer]      
Like a slingshot handle   YSHAPED [as I see it, the handle is I-shaped; the slingshot itself is Y-shaped]   
There were three baseball references today but six weeks before opening day.  
   RATING:    

Three grins = Loved it; Two grins = Enjoyed it; One grin = A bit bland for my taste; One teardrop = Not much fun