Dickwella, who slammed back to back centuries against Zimbabwe in July last year has not managed a half-century in his last 15 innings and also scored just 73 runs in three innings during the Test series against Bangladesh.
The 24-year-old had an opportunity to redeem himself in the T20I series against Bangladesh where he managed a score of 11 in the only game he featured and as a result, has been left from the squad.
Kusal Perera, who returned after recovering from a side strain is expected to take the glove duties while there are also recalls for Nuwan Pradeep, Dushmantha Chameera and Dhananjaya de Silva.
Earlier, Angelo Mathews, Asela Gunaratne and Shehan Madushanka were left out the provisional squad named on Monday due to injuries.
The tri-series will be played between 6th and 18th March with R.Premadasa Stadium in Colombo hosting all the games.
Sri Lanka squad for T20I Tri-Series:
Dinesh Chandimal (captain), Upul Tharanga, Danushka Gunathilaka, Kusal Mendis, Dasun Shanaka, Kusal Janith Perera, Thisara Perera, Jeevan Mendis, Suranga Lakmal, Isuru Udana, Akila Dananjaya, Amila Aponso, Nuwan Pradeep, Dushmantha Chameera, Dhananjaya De Silva
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