The Detroit Lions made strides to improve their running game and secondary this offseason, but now a new hole has opened up that may be difficult to fill.
Left tackle Jeff Backus, who started every game but one over his 12-year career with the Lions, announced his retirement Thursday, according to Michael David Smith of Pro Football Talk.
The 35-year-old Backus may not have been the player he once was, but it's still going to be no easy feat to replace a player who allowed only one sack in 2012.
Here are a handful of options the Lions could explore.
Of the in-house candidates to replace Backus, the early leader in the clubhouse would appear to be Riley Reiff, who started eight games for the Lions last year after being selected in the first round of the 2012 NFL draft.
On the plus side, Reiff didn't allow a sack in his rookie season.
However, this may not be the best solution for the Lions' need at left tackle.
Reiff's skill set would appear much better suited for the right side, and the youngster didn't grade out especially well last year according to Pro Football Focus, ranking 35th among offensive tackles.
Frankly, Backus taking as long as he did to announce his retirement leaves the Lions in something of a bind.
The free-agent market at left tackle is pretty thin at this point. Most of the players that were available have been either franchise-tagged or already signed by new teams.
Of the players that are left on the open market, the best option available is likely Bryant McKinnie.
The 33-year-old started out the 2012 season in a reserve role in Baltimore, but by season's end he was back in the starting lineup for the Super Bowl champion Ravens.
McKinnie's a bit long in the tooth and would be a short-term fix, but sometimes beggars can't be choosers.
A third option for the Lions, should they choose to address their hole at left tackle in free agency, would be to combine the first two scenarios presented here.
Flip Riley Reiff to the left side, and then sign a right tackle in free agency.
However, a second-tier option such as Barry Richardson, who started 16 games for the St. Louis Rams in 2012 and graded out as a top-10 player at his position according to Pro Football Focus, could be a possibility.
The retirement of Jeff Backus certainly threw a monkey-wrench in the Detroit Lions' draft plans, and it greatly increased the chances that the Lions might draft a left tackle at fifth overall.
Of the left tackles available in this year's class, Luke Joeckel of Texas A&M is widely considered the cream of the crop.
The 6'6", 306-pound All-American was the Outland Trophy winner as the nation's top lineman in 2012. NFL.com calls him "maybe the best prospect overall" in the 2013 NFL draft.
Therein lies the problem, as it's a toss-up at best that Joeckel will even be on the board when the Lions go on the clock in April.
That leaves Central Michigan offensive tackle Eric Fisher, who is probably the most likely candidate on this list to be the starting left tackle for the Detroit Lions in 2013.
Fisher has been steadily rising up draft boards since strong showings at both January's Senior Bowl and February's NFL Scouting Combine. As Corey Butzin of MLive.com points out via The Saginaw News, Fisher has drawn comparisons to fellow CMU alumni Joe Staley.
The Lions were in attendance at Central Michigan's recent pro day, and if the 6'8", 304-pounder is available at pick No. 5, there's a good chance that he's going to wind up in silver and Honolulu blue.