Diamondbacks righty Rubby De La Rosa will receive a stem cell injection tomorrow, Nick Piecoro of the Arizona Republic reports on Twitter. The hope is that the treatment will allow him to stave off what would be a second Tommy John procedure.

De La Rosa’s rehab has been something of a rollercoaster: he was able to return briefly, then seemed destined to be shut down, and then seemed like he might be headed back to the major league mound by the end of the season. Now, the situation seems a fair bit more dire than had previously been suggested.

Stem cell and other alternatives to surgery have increasingly been utilized by pitchers hoping to reinforce, rather than replace, their ulnar collateral ligaments. The risk of a TJ procedure failing to produce the desired results is heightened significantly in the case of a second trip under the knife, so the stakes are high in De La Rosa’s case.

Given the timing, a TJ procedure in the near-term would clearly keep De La Rosa out for all of 2017. Second-time UCL replacement recipients tend to take longer to make it all the way back, though he’d at least be reasonably likely to make it back for ’18.

De La Rosa is due a raise — though it won’t be a large one — on his $2.35MM arbitration salary. He’s set for free agency before the start of the 2019 campaign, so the next two campaigns are the final ones of team control for Arizona.

All said, then, there’s a lot riding on De La Rosa’s ability to return. Over his 50 2/3 innings this year, he worked to a useful 4.26 ERA and also showed quite a bit of promise with a rising 9.6 K/9. That makes De La Rosa a critical part of the D-Backs’ rotation picture.