The Toronto Blue Jays head into the 2017 season with a starting rotation that’s projected to be among the best in the American League, but the depth behind that group is a cause for concern.

Team president and CEO Mark Shapiro acknowledged as much during a radio appearance on Sportsnet 590 The FAN Friday morning.

“If you said ‘what’s your one fear heading into the season,’ it probably would be the drop-off from our fifth starter to our sixth starter. That’s not a subtle drop-off,” Shapiro said.

Toronto’s rotation posted an AL-leading 3.64 ERA last season. Aaron Sanchez, Marco Estrada, Marcus Stroman, J.A. Happ and Francisco Liriano form the starting five that will break camp with the team, but should one pitcher miss time, it’s anybody’s guess who will see time as a replacement.

“While we do have guys capable of filling in for two, three, four starts, I’m not sure at (triple-A) Buffalo as we start the season we’re going to have a guy we feel can hop into the rotation and pitch half a year in our rotation and sustain a championship level of starting pitching performance,” Shapiro said on The Jeff Blair Show.

Mat Latos, Casey Lawrence, Lucas Harrell, Jarrett Grube and T.J. House are among the club’s depth options.

Shapiro also shared thoughts on several other subjects while speaking to Jeff Blair and Stephen Brunt …

Mat Latos

One potential starting pitching option at triple-A could be right-hander Mat Latos, who thus far has had an inconsistent spring. The 29-year-old entered Friday with a 6.94 ERA in 11.2 innings, having surrendered eight hits, including four home runs, while walking seven.

Shapiro said the Blue Jays will use as much time as possible to evaluate Latos.

“He’s shown at spots down here that he’s a big-league pitcher. Other times, it’s been a little more inconsistent,” said Shapiro. “You hate to evaluate during spring training but for a guy like that you are … We still have 10 days and we’re going to use that to make that the best decision possible. One of that could be starter in triple-A if that’s something he would accept. The other could be a spot in the bullpen and try to preserve our ability to keep him.”

Latos, an eight-year MLB veteran, agreed to a minor-league deal in February that would pay him $1.5 million if he makes the team, with the possibility of another $500,000 in incentives.

John Gibbons

Shapiro wouldn’t confirm whether the reported contract extension of manager John Gibbons was finalized but did say the club was “optimistic and confident” it would have something to announce by the start of the season.

The president heaped praise on the skipper, who has led the team to consecutive ALCS appearances. “He’s a tough guy,” said Shapiro. “He’s incredibly consistent. And when you talk to major-league players here, elsewhere, historically, one thing they will universally value is a level of consistency from the manager. To know what to expect every single day. Regardless of if you’ve won three, or lost six in a row, he’s the same guy.”

Left field

Figuring out the left-field situation has been a question all spring and Shapiro thinks the Blue Jays have the internal pieces to find a solution.

“You never build the perfect club the day you leave spring training,” he said. “We feel like the group of people we have at first base and left field, we have good answers within here.”

That group includes Ezequiel Carrera — a “darling of the analytics world,” per Shapiro — along with Melvin Upton Jr., Justin Smoak, Kendrys Morales and Steve Pearce, a player Shapiro seems particularly high on. “If you look at his performance it’s actually not good, it’s elite. If he had not had health injuries he would be a $20-million player.”

Shapiro said first base prospect Rowdy Tellez has impressed this spring but still has one hurdle to pass before he can be considered for the major-league team.

“I’ll put the disclaimer on: Rowdy Tellez has never had an at-bat at triple-A,” said Shapiro. “We’re not going to fall into the trap of getting excited by spring training. But there are a lot of things to be excited about with Rowdy Tellez, many of which a fan couldn’t even see.”

Shapiro said he connected Tellez with former big-leaguer Sean Casey, who recently visited Blue Jays camp. Casey, a left-handed hitting first baseman like Tellez, was a career .302 hitter over 12 MLB seasons. Shapiro also noted that Tellez recently took Blue Jays shortstop Troy Tulowitzki out to dinner to “pick his brain and write down six pages of notes.”