TORONTO -- The Blue Jays' starting rotation went from a supposed strength to a noticeable weakness in 2017. Will a similar group bounce back this year?
Well, a lot of that will depend on Aaron Sanchez.
Sanchez is by far the biggest X-factor Toronto has entering the season. When healthy, he arguably has as much upside as any pitcher in the game, but he comes with several major question marks as well. The 25-year-old has just one full season of starting under his belt, but during that 2016 campaign, he finished with an American League best 3.00 ERA. Last year, a lingering blister issue limited him to 36 innings and proved just how unpredictable pitchers can be.
A healthy Sanchez should turn this Blue Jays rotation into one of the best in baseball. An injured Sanchez could have a devastating effect on a staff that still might not have enough depth. Here's a closer look at Toronto's projected starting unit:
ROTATION IF SEASON STARTED TODAY
Marcus Stroman, RHP
J.A. Happ, LHP
Aaron Sanchez, RHP
Marco Estrada, RHP
Joe Biagini, RHP
STRENGTH
The Blue Jays are coming off a season in which they scored the fewest runs in the AL. The everyday lineup remains mostly intact, so it's clear Toronto's rotation will have to steal a lot of games in order to compete with New York and Boston. The top three of Stroman, Happ and Sanchez give the Blue Jays an opportunity to do just that. There's a lot to like here with Happ's dependability and the ability for Stroman/Sanchez to become two of the top pitchers in the Majors.

QUESTION MARK
Which version of Estrada will show up in 2017? He was one of the most underrated pitchers in the AL from 2015-16, but last year, the veteran righty fell on tough times. Citing personal issues off the field, Estrada struggled for most of the year and finished with a 4.98 ERA. That's a far cry from the marks of 3.13 and 3.48 he posted in the two previous seasons, and he needs to regain that form to give the Blue Jays the kind of depth they need from the rotation.
WHAT MIGHT CHANGE
Biagini currently projects as the No. 5 starter, but it's still possible he will open the year in Toronto's bullpen or starting for Triple-A Buffalo. The Blue Jays are in the market for starting depth, and the addition of another proven arm would certainly change things for Biagini. A major addition such as Jacob Arrieta, Yu Darvish or even Alex Cobb does not appear to be in the cards, but a second-tier free agent remaines a possibility.
The Blue Jays likely would be well served to avoid using Biagini in the rotation at the start of the year. He has spent the past two seasons with the big league club, but almost all of that work came out of the bullpen, where he did not pitch out of the wind-up. If Toronto is intent on using him as a starter, there's a clear benefit to having him begin the season with Buffalo and continue to work out the kinks in his delivery. His presence as a depth piece also would allow the Blue Jays to manage injuries more effectively.