Mark Teixeira and Greg Bird have combined to be elite

Even the most optimistic Yankees fans probably weren't expecting much from Mark Teixeira this season. The combination of his various injuries with a steady decline in production since 2011 set the bar pretty low. Then a funny thing happened. At 35, Teixeira rediscovered his power stroke and over the first four and a half months of the season he produced like the big gun the Yankees are paying him to be. His slash stats were the best they'd been in years. He was walking more, striking out less, and he eclipsed the 30 home run mark after a three year drought. The real Teixeira was back.

That is, until a major injury derailed his season yet again. In mid-August a foul ball off his shin turned in to a bone bruise which turned into a broken leg which meant Teixeira was done for the year. The feel good story of 2015 for the Yankees seemingly had a tragic end. Or did it? Waiting in the wings to replace Teixeira was a tall, lean, lefty slugger named Greg Bird who had cut through Double and Triple-A pitching like a hot knife through butter. Bird was plugged into to the everyday first base job and had an almost immediate impact. In his fifth career game he was the difference as he hit a pair of two-run homers in a 4-3 win against the Twins.

Since then Bird hasn't looked back, hitting major league pitching with relative ease. Thanks to his bat, the Yankee offense has remained among the American League's best even after losing their strongest hitter in Teixeira. In fact, if you were to combine the production of Bird and Teixeira, the Frankenstein monster that results ranks among the elite MLB first basemen this year. MLB first basemen ranked by 2015 wRC+ (data courtesy of Fangraphs):

Among this group the Teixeira/Bird duo is top in isolated power, and only Chris Davis has more home runs and RBI than them. Greg Bird has been nothing short of amazing filling in for the resurgent Teixeira and if he's holding his own with the names in the table above at just 22 years old, the Yankees could have something special on their hands.

In the bigger picture, Bird's arrival also means the Yankees have a cheap insurance policy for the oft-injured Teixeira heading into the final year of his contract. Should Teixeira miss any extended time in 2016, Bird can step in with little to no drop off in production. If Teixeira somehow remains healthy, then it will give Bird the opportunity to fine-tune his offensive game for another season in Triple-A. He's proven he can handle the two most important aspects of hitting -- drawing walks and putting the ball in the seats -- at the major league level, but he could stand to boost his batting average, and he should also look to strike out less. By 2017 we could be looking at a polished lefty masher entering his prime at the heart of the Yankee order.