You can be 99% sure to catch Bhagalpur Express since Matsyagandha Express reaches LTT around 15-30 min late usually. Ocassionally its arrival will be delayed by an hour. But even in this case you can board Bhagalpur Express after having a nice breakfast at LTT.
Beware its going to be scary. Sometimes Konkan railway route is so unpredictable that perhaps twice/thrice a year, trains are delayed by more than 3 hours.