Club Career
After playing his collegiate soccer at Duke University from 2005-2008, Grella was the 34th overall pick in the 2009 MLS SuperDraft by Toronto FC. Instead of signing with the Canadian club, Grella looked towards Europe and landed a trial with Leeds United.

The former UEFA Champions League semifinalist were impressed with Grella' efforts in a reserve match and signed the striker to a contract through the 2009-2010 season.

Grella made his debut for Leeds in February 2009 coming on as a substitute in a 1-0 loss against Huddersfield Town. By August, he signed a contract extension.

During the 2009-10 season, Grella was a highly-regarded reserve, but was unable to beat out the experienced and highly-rated duo of Jermaine Beckford and Luciano Becchio for a starting role. Grella spent the season as a frequent substitute.

Due to personnel changes and a lack of a true breakthrough moment, Grella found himself out of Leeds' immediate plans in the beginning of the 2010-11 season. After struggling to break into the matchday squad, the young striker was loaned out to Carlisle United until the end of December.

By the summer of 2011, Leeds manager Alan Grayson had made it clear that Grella was not in Leeds' first team plans, giving the forward the green light to find a new club. In late August, Grella signed with Brentford of League One.

Grella found it difficult to get on the field with Brentford and parted ways with the club by mutual consent midway through the season. He signed on with Bury for the second half the year and found more success, netting eight goals in all competitions.

In the summer of 2012, Grella signed on with yet another English lower-league club, Scunthorpe United.

International Career
Grella has made appearances for both the United States Under-18 and Under 20 teams. Grella was hoping to be part of the U-20 Team at the 2007 U-20 World Cup in Canada, but coach Thomas Rongen left him off the roster.