Reason to be wary about Hanrahan?

The Red Sox acquired their 2013 closer by trading for Joel Hanrahan last week, a decision likely based on the 36 saves and 2.72 ERA he posted last year. But does he really have the stuff of an elite ninth-inning guy?

Let's look closer at his stats.

Hanrahan’s sub-3.00 ERA and batting average allowed of .187 were supported by an unusually high strand rate and low BABIP, two factors that will make it difficult for Hanrahan to replicate his 2012 season in 2013.

His percentage of baserunners stranded (89.7 percent) and BABIP (.230) both ranked in the top five among NL relievers with at least 50 innings last season and were far removed from his career averages of 75 percent and .306.

Though Hanrahan had an above-average strikeout rate in 2012, his walk rate jumped from six percent in 2011 to 14 percent in 2012 (fifth-highest in MLB) and his groundball rate fell by nearly 15 percentage points over the last two seasons.

This combination of statistics partly contributed to a 4.45 FIP (an ERA estimate based on strikeouts, walks, and home runs allowed), which ranked 118th out of 134 relievers with at least 50 IP.

The difference between his ERA and FIP was 1.74 runs.

What does that mean for Hanrahan’s 2013 campaign?

Hanrahan explained this past Wednesday that the ankle injury he suffered late last season forced him to wear a tight brace that restricted his mechanics. He said he doesn’t believe the walks (which rose from 16 in 2011 to 36 in 2012) will be a concern in 2013.

The Red Sox said they looked very closely at the reasons for the increase in walks for Hanrahan. In fact, manager John Farrell already has spoken with Hanrahan about correcting those numbers. Hanrahan will also speak with Red Sox pitching coach Juan Nieves and bullpen coach Gary Tuck at some point this offseason.

"It's not something we're concerned about long term," assistant GM Brian O'Halloran said. "We believe we're going to get the guy that has been a great closer for two years. Although we did pay close attention to (the walks) and looked into that, we feel very comfortable and confident he will be a very good closer for us going forward."

In 2011, five relievers with at least 50 IP had a FIP that was at least 1.5 runs higher than his ERA, and then pitched at least 35 innings the following season (Luis Ayala, Scott Downs, Alfredo Aceves, Eric O’Flaherty, Francisco Cordero).

Each of them, except for Ayala, had their ERA nearly or more than double in 2012.

Information from ESPNBoston.com’s Joe McDonald was used in this report.