It's amazing that no one has signed Keuchel.
Arrieta signed with the Phillies one-year ago today (March 11), and he started the season just over one week late (game 8). This season starts a little earlier than last year; so, Keuchel is now in the danger zone as for each day he doesn't sign, that is part of the season that he will miss which makes him less valuable (teams aren't going to want to pay a pitcher full price for 2019 if he can only pitch part of the season).
Not as much of risk as Kimbrell as it may not take a reliever as long to get ready for a season.
Other notable FAs that have not signed yet:
Carlos Gonzalez
Joey Bats
Bartolo Colon (someone must want Big Sexy)
Yovani Gallardo
Evan Gattis
Gio Gonzalez (starter a playoff game last October)
Chase Headley
Edwin Jackson (was effective for the A's last year)
Austin Jackson
Adam Jones (reportedly close to a deal with D'Backs)
Ryan Madson
Brandon Phillips (beat the Braves last year)
AJ Ramos (closed for the Marlins in 2018)
Jose Reyes (he has sucked for a while)
James Big Game Shields
Tony Sipp (everybody needs a LOOGY)
Danny Valencia
Chris Young
You could field a team with the current FAs and be better than the Orioles.