The questions about the Red Sox rotation abound.

Can Josh Beckett bounce back? For that matter, how might the mild concussion he suffered on Monday impact his preparation to do so?

Can John Lackey sustain his promising second half?

Can Clay Buchholz build on his extraordinary performance from a breakout 2010 campaign?

Can anyone ever make sense of Daisuke Matsuzaka?

Will the Sox have adequate rotation depth should any of their starters go down?

These are all fair inquiries, and all reminders that what appears to be a loaded Red Sox team on paper could have a rotation that is either a tremendous strength or, potentially, a shortcoming. But amidst those questions, there is one certainty.

There is Jon Lester.

The 27-year-old will make his first start of the Grapefruit League season on Tuesday against the Twins. In all likelihood, it will be a non-event.

After the performance – whatever his line in the exhibition game – Lester will shrug about what he is and is not working on in spring training; he will find fault with some aspect of his outing (he is, after all, a perfectionist); he will sigh when asked after the contest about trying to escape his April struggles; he will leave the ballpark as if punching out of work for the day, ready to return on Wednesday.

This is who Lester is. He embraces the process and routine of pitching, quietly demanding a great deal of himself but rarely showing any use for or interest in celebrating his accomplishments.

Yet for the Sox, Lester has become arguably the most important player on the team. He is now three years into a run as one of the top starters in the game. April struggles notwithstanding, he has delivered consistent dominance despite residing in the toughest division in the game.

He’s won 16, 15 and 19 games over the last three seasons; he’s made either 32 or 33 starts while tossing 200-plus innings in all three campaigns; he has three straight years of sub-3.50 ERAs.

He has established himself to such a degree – and with such a remarkable array of pitches that allow him to carve up both sides of the plate to both right-handed and left-handed hitters – that his excellence in any given start is almost taken for granted.

John Lackey believes that his rotation-mate is the best starter in the game. Even Sox officials take for granted that the young southpaw will give them a huge advantage on almost any night he starts.

“I’m surprised every time he gives up runs,” admitted GM Theo Epstein. “I think he’s just about the best left-hander in baseball. … There are 30 teams, there should be 30 No. 1s. There probably aren’t. But he’s clearly [deserving of that title].”

It would be difficult to argue the point. Over the last three seasons, Lester is one of just four pitchers to have 50 wins, joining Roy Halladay (58), CC Sabathia (57) and Adam Wainwright (50). Of course, Lester is the only one to have racked up all of his victories while in the American League.

He is, moreover, just the third AL pitcher since 2000 to win 50 or more games in his age 24-26 seasons; he is the first Sox pitcher to accomplish that feat since Roger Clemens.

His 3.29 ERA is 15th in the majors among pitchers with at least 300 innings pitched over the last three years. Of those in front of him, only Mariners ace Felix Hernandez (who plays in a great pitcher’s park) and Zack Greinke – who was an AL Central resident with the Royals until being dealt to the Brewers this winter – spent all three seasons in the AL. That helps to explain how his ERA+ of 139 is tied with Sabathia for ninth best in the majors over the last three years.

Strikeouts? He ranks seventh in the majors with 602 over the last three years, and his 8.7 strikeouts per nine innings ranks second (to Justin Verlander) among American League pitchers.

When he was coming up through the Sox farm system, they saw a pitcher whom they thought could develop into a front-of-the-rotation starter. But even they could not predict what the young left-hander has become.

“I think we knew he was going to be a big strong horse with power stuff,” said Epstein. “We saw the physical ability, the clean delivery, the way the arm worked, power stuff. The glove side of the plate was a lot more advanced than the arm side. We weren’t sure how all the parts were going to fit together, but we trusted him to figure it out because he had such great raw materials.

“But the way he’s advanced his career, become so polished at the big league level, so mature, it’s impressive. It’s hard to foresee that with anybody.”

That was then, this is now. Lester has a clearly established baseline as an elite starter. The Sox can now take his sustained excellence going forward – barring injury – as something of a given.

He is young, durable and at a point where he can consistently harness his abilities into outstanding performances. He is also a bargain, as he will make a $5.75 million base salary this year in the third year of his five-year, $30 million deal that includes a team option for 2014.

That combination of traits carries exceptional value to the Sox. Indeed, the team views the combination of Lester and fellow farm system product Buchholz as being perhaps its most valuable asset, a pair of young pitchers with ace-caliber talent that simply could not be replaced at their current minimal cost had they not been cultivated from within the system.

“It’s very meaningful. Just to have two homegrown guys in our rotation now changes the landscape of our franchise, for me,” said Epstein. “You don’t want to live in free agency with starting pitching. To have Buchholz and Lester, I haven’t looked at it, but it’s probably as good a homegrown pair of starters as there probably is in the game. Everything else plays off of that as far as roster construction.”

In that sense, it is not just an ace but an anchor who will take the mound in Grapefruit League action on Tuesday. Lester is the one Sox starter whose performance can be taken as a near-given, making him a cornerstone of what the Sox hope to build in 2011 and for years to come.