Andrew Lewis will captain the Blues when he plays his 250th game for Cardiff and the Blues this evening.
Alp leads a side against the Scarlets that has now been finalised after releases from the Wales Six Nations' camp.
Fly-half Nick Robinson goes into the game needing just two points to reach the 200 mark for the season.
Blues team v Scarlets: Craig Morgan; Nick Walne, Jamie Robinson, Pieter Muller, Jonny Vaughton; Nick Robinson, Ryan Powell; John Yapp, Andrew Lewis (capt), Ben Evans, Craig Quinnell, Andy Moore, Matt Cockbain, Nathan Thomas, Robin Sowden-Taylor
Replacements: Ken Fourie, Rhys Thomas, Heino Senekal, Jim Brownrigg, Dan Baugh, Andrew Moore, Matt Allen
Rob Appleyard has been suspended for 21 days (until 31 March) by a WRU Disciplinary Committee following his sending-off against Leinster Lions last week.