There probably isn't any one player on the Tampa Bay Lightning roster that draws more vitriol than Matt Carle.
Since signing with the Bolts as an unrestricted free agent in the summer of 2012, Carle has slowly gone from "nice free agent pickup" to "horrible waste of cap space" in the eyes of many Tampa Bay Lightning fans.
It's fair to say Carle has underperformed expectations for him when he signed with the Lightning, but it's also important to point out that those expectations were in part created from salary he's being paid. Paying for roster players in unrestricted free agency is "overpaying" more often than not, which is why so much of the Tampa Bay Lightning's success under Steve Yzerman has focused on drafting and development, with cost-controlled assets on ELCs and RFA deals.
Remember, though, the composition of Tampa Bay's NHL blue line prior to free agency in 2012; it featured names like Brett Clark, Keith Aulie, Bruno Gervais, and Brian Lee, not one of which is still taking a regular NHL shift in 2015. Carle's deal was an overpay, but he was an immediate and necessary upgrade for a Lightning team that needed to get better both in the present and in the future.
He's scored 71 points in 189 games in three seasons since signing with the Bolts, which isn't dominant offensive performance but is certainly more production from the blue line than anyone else for Tampa Bay save Victor Hedman. He's still a capable puck-mover that makes good passes in transition more often than not, and he had a really good regular season skating primarily with Anton Stralman, Jason Garrison, and Mark Barberio.
Some of the growing ill will towards Carle can be attributed to recency bias; his performance in the playoffs ranged from "underwhelming" to "holy crap Matt what are you even doing out there". It's important to remember, however, that he was tasked, for the first time all season, with playing mostly with the oft overmatched Andrej Sustr, who still looked quite green against the best forwards the NHL has to offer. Shifts spent with Anton Stralman or his former Flyers teammate Braydon Coburn showed he still has the ability to play in the top-4 and be a boon rather than a burden. But far too often Carle and Sustr simply could not get on the same page in the defensive zone, leading to horrific breakdowns and crippling goals against.
Unfortunately, that result was probably predictable, and it's a shame the Lightning weren't able to avoid it. Driving his own pair is not something Carle was asked to do during the regular season with much regularity, and in fact, since he was signed, he's been best when used as a complementary player in the top-4 rather than being asked to carry a pair himself. Put simply, he's a good partner, but not necessarily the type of elite blue-liner that makes his partner better (see: Victor Hedman, Anton Stralman).
5v5 Goals For%, Matt Carle: w/ Stralman (344:07) 59.3% w/ Garrison (141:57) 66.7% w/ Barberio (117:45) 62.5% w/ Sustr (114:33) 37.5%— Kyle Alexander (@kalexanderRC) June 18, 2015
That's okay, though, and it doesn't mean Carle's a waste and Tampa Bay needs to look to trade him. The Anton Stralman contract worked out like gangbusters for the Lightning, but comparing that deal to Carle's doesn't seem right. Stralman might have been the best UFA signing in the NHL in some time. It's an unfair comparison. And when Stralman and Carle play together, Tampa Bay has seen very good on-ice results in terms of shots, goals, and scoring chances.
The Tampa Bay Lightning roster, as it is constructed today, is better off with Matt Carle on it. 2016-17 might be a different story, with a likely extension for Steven Stamkos taking up a significant percentage of the cap and extensions needed for other key forwards. Looking to trade him then makes more sense developmentally, too, with another year of seasoning for left side defenders like Slater Koekkoek and Nikita Nesterov. But for right now, Carle is an important cog on a team that almost went the distance. Why break that up before you absolutely need to?