Just looking at Toronto's roster and it was heavy LH shots.
W: Blake (LH) - Ponikarovsky (LH) - Hagman (LH) - Kulemin (LH) - Steen (LH) - Mayers (RH)
C: Grabovski (LH) - Stajan (LH) - Antropov (LH) - Moore (LH)
It was Nik Kulemin's rookie year and I seem to recall he was a well-regarded prospect. Not sure if Steen lost time as a result. Colaiacovo seemed to be a tweener and found a role in St. Louis.
Maybe reminds me of Anaheim indirectly swapping Kyle Palmieri for Carl Hagelin at the 2015 Draft. Palmieri was behind Perry/Ryan, so the thought was that they were swapping a 3RW for a 2LW. Didn't quite work out.
So perhaps the Leafs thought the same that they were adding a 2RW in Stempniak.
1999 Devils were also mostly LH shots, early in that season Lou swapped Brian Rolston for Claude Lemieux. And last year's Devils were similar, part of the reason they swapped out Yegor Sharangovich for Tyler Toffoli so they could have a RH shot up front on the PP.
Edit: Quick peek at the spring 2008 THN Future Watch and Kulemin was the #24 ranked prospect league wide. Looking at some of Steen's final games as a Leaf and he was dipping below 15 minutes in a few of them.
Get the latest box score updates on the Toronto Maple Leafs vs. Vancouver Canucks game played on November 15, 2008 on Hockey-Reference.com
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Wingers: Kulemin (16:31), Ponikarovsky (16:27), Hagman (16:14), Blake (14:09), Mayers (13:32), Steen (11:53), Hollweg (7:16)
Get the latest box score updates on the Atlanta Thrashers vs. Toronto Maple Leafs game played on November 25, 2008 on Hockey-Reference.com
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In Stempniak's first game as a Leaf, he posted 17:16.