Bangladesh pacer Mustafizur Rahman gave his team another breakthrough when he sent back Ireland batsman Niall O’Brien for 30 off 42 balls to leave the hosts 116 for four in 27.3 overs.Mustafiz struck early in the innings when he got opener Paul Stirling out for a duck before Mosaddek and Shakib picked one wicket each.Earlier, Bangladesh captain Mashrafe Mortaza won the toss and opted to field first against the host in the fourth match of the Tri-Nation Series at Dublin (Malahide) on Friday.Bangladesh: Tamim Iqbal, Soumya Sarkar, Sabbir Rahman, Mushfiqur Rahim(w), Shakib Al Hasan, Mahmudullah, Mosaddek Hossain Saikat, Sunzamul Islam, Mashrafe Mortaza(c), Rubel Hossain and Mustafizur Rahman.Ireland: William Porterfield(c), Paul Stirling, Ed Joyce, Niall O’Brien(w), Andrew Balbirnie, Kevin O’Brien, Gary Wilson, George Dockrell, Barry McCarthy, Tim Murtagh and Peter Chase.