"The Blue Jays, a team deep in high-end pitching prospects, have expressed strong interest in trading for Diamondbacks right fielder Justin Upton, major-league sources say.

The Jays, after winning 85 games and finishing fourth in the highly competitive AL East last season, are showing a renewed aggressiveness this offseason.

Upton, 23, would be a more logical fit than second baseman Dan Uggla, whom the Jays tried to acquire from the Marlins earlier in the week.

While Uggla stood to earn $10 million-plus in arbitration and then become a free agent, Upton is under contract through 2015 and guaranteed $49.5 million over those five seasons.

The Red Sox, thought to be a possible front-runner in the Upton trade discussions, are now on the "backburner," sources say.

Roughly half the major-league clubs have expressed interest in Upton. The Diamondbacks are making it clear to potential suitors that they intend to "win" any Upton trade.

An official from one interested club said the D-Backs want four top prospects for Upton. The Yankees, among other teams, are balking at that price.

The Diamondbacks, judging by the level of interest, are confident a deal is possible, sources say. Upton's contract enables him to reject trades to four clubs, but his list is not expected to be a factor.

The Red Sox are interested in Upton, but also working multiple fronts, including the pursuits of free-agent outfielders Carl Crawford and Jayson Werth, and their own free agents, catcher Victor Martinez and third baseman Adrian Beltre.

The Diamondbacks have discussed expanded deals involving other teams with the Red Sox, sources said. But as of Wednesday night, there was little momentum for a trade."