St. Louis Blues general manager Doug Armstrong's summer shopping list included a number of restricted free agents to consider bringing back next season. But being heavily under the salary cap ceiling and having over $20 million in cap space, according to CapGeek, will allow him to invest in the franchise's future.

After re-signing Patrik Berglund on Tuesday for one year, Armstrong gave Kevin Shattenkirk, one of his two lynchpins on defense, a four-year, $17 million extension, according to Jeremy Rutherford of the Post-Dispatch.

Shattenkirk has averaged 21:27 of ice time per game and 7 goals and 33 points over the last two seasons since coming over in a trade with the Colorado Avalanche in 2011.

With Shattenkirk locked up, that leaves remaining two big Blues RFAs remaining with Chris Stewart and Alex Pietrangelo. Armstrong told Rutherford on Tuesday that one negotiation won't affect another, which is true; but in Pietrangelo's case, his negotiations will certainly be affected by the recent re-signings by Roman Josi and Slava Voynov, as well as what Kris Letang might re-sign for in Pittsburgh (or elsewhere).

Basically, Pietrangelo is about to get paid.

Follow Sean Leahy on Twitter at @Sean_Leahy

NHL video from Yahoo! Sports:

Related coverage on Yahoo! Sports:
• Marian Hossa won't get buyout from Blackhawks
• Lightning buy out captain Vince Lecavalier
• Scouts rate the top 10 NHL prospects