This was not the kind of entry into the Red Sox record books that Josh Beckett could have ever envisioned.

Amidst an exceedingly difficult season that has seen the Opening Day starter struggle to be healthy (he missed more than two months with a back strain) or effective, the right-hander has rarely found the form that had characterized his first four years in Boston (and particularly his three most recent campaigns, from 2007-09).

It is worth looking back at Beckett’s pre-2010 resume, if only to offer a contrast to his disappointing 2010 season. During that time, it has been sometimes forgotten this year, Beckett had compelling credentials as a front-of-the-rotation starter, a two-time All-Star whose performance earned him a four-year, $68 million contract extension from the 2011-14 seasons.

From 2006-09, Beckett was tied for third in the majors with 65 wins. His 3.71 ERA from 2007-09 ranked third among pitchers who threw at least 450 innings while working exclusively in the American League. His 8.66 strikeouts per nine innings ranked sixth in the majors from 2007-09.

This year, obviously, has been another story. Despite pitching in front of an upgraded defense, Beckett (4-3) is allowing a career-worst 10.4 hits per nine innings. His 1.4 homers and 2.9 walks per nine frames are the second worst marks of his career.

But the most eye-popping number tells a blunt tale of his struggles. Beckett’s 6.50 ERA is not merely the worst of his career. It has put him in reach of an ignominious sort of Red Sox history.

Right now, Beckett’s ERA is the eighth-worst ever by a Sox pitcher who has thrown at least 75 innings. (For the list, “topped” by Jim Bagby with a 7.09 ERA in 1939, click here.) Even more surprising, Beckett has a shot at producing the worst ERA ever by a Sox pitcher in a season in which he throws 100 or more innings. That mark is held (quite unexpectedly) by Hall of Famer Lefty Grove, who suffered through a dismal first year in Boston in 1934, producing a 6.50 mark.

If there is a silver lining for Beckett and a Sox team that has him under contract for the next four years, it is that some of the pitchers on this list have recovered in subsequent years to produce outstanding seasons.

Grove is the most noteworthy example. After his horror show of a Sox debut in ’34, he led the American League in ERA in four of the next five seasons. Buchholz, of course, went from a 6.75 ERA in 2008 to the lowest ERA (2.21) in the majors this year. Bagby went on to produce a couple of 17-win seasons in which he had ERAs around 3.00.

And so, there would be precedent for Beckett to leave behind his struggles of 2010. For that matter, there remains time for him to do so this season. After all, he will still show in stretches the impressive stuff that helped lead to his emergence as a leader of the Sox pitching staff over the last few years.

One of the great puzzles of his season is the fact that his pitches will show plenty of life, at times overpowering hitters for a few innings at a time, before he suddenly sees an outing fall apart in a big inning. That has been the case in his most recent two outings. If Beckett can harness his effectiveness for a full outing, then he might well be able to remove himself from the running for one of the worst ERAs in Red Sox history.

Even so, it is nothing short of stunning that, as Beckett prepares for his start against the Orioles on Tuesday, his season has a chance to rank as one of the worst in franchise history.