The Toronto Blue Jays appear set for a busy offseason as they're reportedly 'very aggressive' in their pursuit of left-handed reliever Andrew Miller, according to Jeff Blair of Sportsnet.

Miller is one of the top relievers on the open market and would be a significant upgrade to a Blue Jays' bullpen that struggled mightily in 2014.

The 29-year-old is coming off a career-year and is no stranger to pitching in the American League East, having played for the Boston Red Sox for the last four seasons before a deadline deal in July brought him to the Baltimore Orioles.

Miller, who is said to be in search of a four-year deal, posted a 2.02 ERA and 103 strikeouts in 62 1/3 innings last season while holding opposing hitters to a .153 average.

Converted to a reliever in 2012, Miller has stated that he isn't demanding to be a closer, though Casey Janssen's departure leaves an opening for the Blue Jays. As many as six teams have been reportedly interested in Millers services.

Toronto inked catcher Russell Martin to a five-year, $82-million deal earlier on Monday.