Mike Wallace and the Vikings: What went wrong?

Exactly one year ago from this coming Sunday, news broke that the Vikings had traded for wide receiver Mike Wallace. Minnesota sent a fifth-rounder to the Dolphins in exchange. They got back a seventh-rounder and a receiver in Wallace who carried a hefty salary to go with some pretty nice credentials.

The Vikings soon cut veteran Greg Jennings to make room for Wallace. The hope was that Wallace would inject life into the Vikings' passing game, particularly as a deep threat. That never materialized.

And as a result, after a lackluster season in which Wallace caught just 39 passes and saw his role diminish as the year went on, the Vikings for the second consecutive offseason cut a veteran receiver who didn't make the as-advertised impact. The Vikings saved $11.5 million on the salary cap, money they are starting to invest in outside free agents like guard Alex Boone of the 49ers.

Before we get too far into the future, though, let's take one final look at the past and why things didn't work out with Wallace in purple — not merely as a means of rehashing the 2015 season but to assess what might/should happen going forward.

Football, after all, is a team sport. It often takes a lot of moving parts to succeed or fail. When we say "Mike Wallace had a disappointing season" we really mean a lot of things:

1) Teddy Bridgewater was not accurate on deep passes, nor did he throw a lot of them. Bridgewater is a very accurate short passer. But if Wallace was signed ostensibly to stretch the field, he was paired with a QB for whom that is not — at least not yet — a strong suit. Bridgewater attempted just 13 passes last season that traveled more than 30 yards beyond the line of scrimmage in the air. He completed just two of them. In his rookie season, Bridgewater was 2 for 22 on such passes. In the two seasons combined, he had two TD passes that traveled 30 yards or more.

In contrast, Wallace's old QB Ben Roethlisberger in Pittsburgh — where Wallace had his best seasons, a pair of back-to-back 1,000-yard efforts in 2010 and 2011 — attempted 33 such passes in 2015 and completed 13 of them. In 2010 and 2011 combined, Roethlisberger had 8 TD passes that went 30 yards or more in the air.

2) Poor offensive line play. Not all of that is on Bridgewater, of course. You could reasonably argue that offensive line play was a larger culprit in preventing the Vikings from attempting and completing deep passes.

Late in the season, Bridgewater topped all NFL QBs in the percentage of dropbacks on which he faced pressure — nearly half of them. You can't throw deep if you don't have time. This is one of the 823 reasons the Vikings must improve their offensive line dramatically this offseason. Signing Boone is a start, but more work remains.

3) The offensive philosophy shifted to a more conservative approach early in the year. Wallace, through four games, had 20 catches. He was on pace for 80 grabs and more than 900 yards. But somewhere around the bye week — which came after those four games — the Vikings' offensive approach became even more conservative and run-oriented, with more snaps under center to better use Adrian Peterson. In the next seven games, Wallace had 8 catches combined, for fewer than 100 yards. The Vikings won six of those games, so the method was working. But it left Wallace with little to do.

4) The emergence of Stefon Diggs. Just as significant to the reduction in Wallace's production as the shift in offensive philosophy was the emergence of rookie wide receiver Stefon Diggs. Diggs was inactive for the first three weeks. Over his next four games, he averaged more than 100 yards receiving. There was really only room for one wideout to have big numbers, and Diggs started clicking with Bridgewater. Whether Diggs' emergence or Wallace's downfall precipitated that switch is unclear.

5) Wallace is possibly on the decline. Wide receivers are at their peak production when they are around 26-27 years old, according to this from Pro Football Focus. It's possible that Wallace — who averaged more than 1,000 yards per season in his five years between the ages of 24 and 28 — started a period of decline last year at age 29, when he caught just 39 passes for 473 yards. A deep threat who loses even half a step suddenly isn't as threatening (or potentially open) as he once was.