The latest bit of AL upending came Friday, when the Astros reportedly agreed to a deal with free-agent first baseman Christian Walker. Were this a normal offseason for the 'Stros, Walker would simply be filling the hole that Jose Abreu had struggled to fill and sliding into a loaded lineup. But instead, this has been the offseason, more than any other in this era of Astros excellence, that has tested Houston's staying power as an AL West force as the realities of age and earning power catch up to their core. And so the Walker signing signals so much more.