No roster can be made bulletproof — after all, the long season will expose every weakness and create new ones via injury and/or under-performance. That does not deter clubs from trying to address vulnerable areas. The Yankees know they might be good enough to line up with what they have now and be strong contenders while preserving their prospect base and some financial flexibility to problem-solve during the season. But they also know their rotation contains age (CC Sabathia), injury history (Sonny Gray and Masahiro Tanaka) and larger 2017 major league innings workloads than anticipated (Jordan Montgomery and Luis Severino). An injury and a regression in April could set them on a bad path. That is why they wanted to sign Shohei Ohtani and, when that failed, trade for Gerrit Cole, who instead went to the Astros. That would have allowed them to either go with a six-man rotation or put Montgomery at Triple-A with Chance Adams, Luis Cessa and Justus Sheffield to have depth when calamity strikes. In addition, the Yankees believe Gleyber Torres and Miguel Andujar are their second and third basemen of the future. But is that now? And if not, can some combination of Thairo Estrada, Jace Peterson, Ronald Torreyes and Tyler Wade adequately cover both sides of the ball? One more veteran who could play second and/or third would provide greater comfort. Looming over all decisions is the Yankees’ pledge to stay under the $197 million luxury-tax threshold in 2018. To that end, I have a suggestion: See if a trade could be built around sending Jacoby Ellsbury to the Rockies for Ian Desmond. Desmond has four years at $63 million remaining (including a $1 million assignment bonus if traded). Ellsbury has three years at $68.4 million left.