I think Army made a really good move signing Lehtera (along with Stastny) and NOT trading off a bunch of future player assets for Spezza. Spezza is ready to start the downside of his career, already having inury troubles, which would have been more compounded this season, had he joined The Blues to play in The West. Also, Spezza's defence is pretty weak.
When some of our Russian, Finnish and Swedish Blues' fans were raving over Lehtera a few years ago, hoping The Blues would sign him and play him then, I was a bit skeptical. He always had great vision, and was a great passer. But his skating was laboured, both in acceleration and straightaway speed. And he didn't play defence well. Over the past 2 seasons, he has improved on both. He accelerates much better (about average now) and his straightaway speed is now above average (fairly good). He also is much improved on defence. Should be about average for an NHL centre (which will be fine, if his passing nets a bunch of assists for Tarasenko and Schwartz, or even if he helps Berglund to again rise above 20 on Line 3).
I expect that he'll need a little time to adjust to The NHL's smaller rink, but, because of his previous chemistry with Tarasenko, I think he'll be an effective player from the start, or very early in the season. I don't see him being a bust. It's just a matter of whether or not he plays on the "de facto" "2nd" (with Schwartz and Tarasenko) or "3rd" Line (Berglund and Tarasenko).
He does have a big weakness, in that he's hesitant to shoot. He passes up good opportunities to pass again. That really hurts on The NHL level. But, I'm hoping that Hull, and/or MacInnis can work with him on his shot, to give him confidence. In The KHL and Finnish Elite Leagues, he's averaged 3 assists for every goal. But, his overall scoring numbers have been good. Remember that in The European leagues, secondary assists are awarded much less than the "almost automatic" 2 assists per goal in North America.
I look forward to seeing how he plays in Camp, the preseason and early season, and how that plays into how the team's mid/late season and playoff lines will shake out.