DeSmith was an option the Leafs had been loosely linked to by Chris Johnston of TSN had he hit the open market. The main reasoning was because of his low cost and the Leafs' cap crunch. DeSmith has played 96 NHL games in his career but has posted a very respectable save percentage of .916 and goals against average of 2.62.
DeSmith is exactly the type of goalie the Leafs will likely end up pursuing in the off-season if the rumours about what they're considering are true. A report last month suggested that the Buds could look for a pair of goalies who are both in and around the $1M-$2M range who have yet to break out. The idea would be to run a ~$4M tandem rather than spending big on a starter.
Given DeSmith's career numbers, he certainly looks like he is on the verge of a breakout campaign, but is stuck behind Tristan Jarry in Pittsburgh for the next couple of seasons. The Leafs will have to continue to search elsewhere for their next starter/tandem if they don't reach an agreement with Jack Campbell.