When NHL teams rent players with expiring contracts at the trade deadline for draft picks, how far can we expect them to advance in the playoffs based on the round of the pick they traded? The sample will only include roster players who are becoming UFAs in the salary cap era, excluding hockey trades where a permanent asset is coming back with the rental. These do need to be players of some significance, not minor leaguers. There were 131 trades since 2006 that met my parameters. Over half the teams to win the Stanley Cup since the salary cap did not make any significant deadline rental. Some of those teams had made rentals earlier in the season, not waiting until close to the deadline.
In the chart below, you can see the pick distribution by round.
First round picks are the rarest commodity to be traded in the 48 hours leading up to the NHL trade deadline. We saw an increase in 2018, though most of those were for players with term remaining on their contracts, not pure rentals. We will see in the following graph that teams trading 1st round picks in the rental market do fare better in the playoffs, but note that it has a substantially smaller sample size than the other categories. Not all the premium players acquired for first round picks made a significant contribution to the team's success, but some did. Dwayne Roloson played a major role getting Edmonton to the Cup final in 2006, whereas Jaromir Jagr finished 7th in playoff scoring for the 2013 Bruins.
I might have expected more 6th and 7th round picks, but applying the parameter "player of some significance" to the sample did exclude some less significant transactions.
The chart below shows how far teams who trade certain picks will advance in the playoffs, from 2006 to 2017.
Those teams trading 1st do tend to finish higher in the standings than teams who trade 2nd rounders, ergo they were probably a better team to begin with, and that's why they are willing to part with a 1st. While 40% of teams who traded a 1st advanced to the conference finals, 0% won the Stanley Cup. Most eventual champions are trading 2nd, 3rd, or 4th rounders, if anything at all. This could just be a coincidence, or perhaps teams who are desperate enough to trade a precious 1st rounder have flawed rosters. 80% of the 1st rounders traded for rentals occurred prior to 2009, so teams were more willing to trade them earlier in the cap era. It has become less trendy over time.
The quality of the pick traded depends on the quality of the rental coming back. There is some evidence to suggest that trading a 1st rounder for a deadline rental does help a team win a round or two, but does not significantly boost their chances of winning a Stanley Cup. The sample size of the 1st round rentals is 10, which is too small to say definitively that there is a cause and effect relationship between 1st round rentals and playoff success. There is at least "evidence to suggest", and I may need to expand the parameters to include hockey trades in order to obtain a sufficient sample size for trading 1st rounders.