As you can see from the No. 20 list at CubsByTheNumbers.com, that uniform number doesn't have a stellar history:
Roy Johnson (coach, 1937-39), George Uhle (coach, 1940), Emil Kush (1941), Hank Gornicki (1941), Stan Hack (1943), Don Johnson (1943-48), Dewey Williams (1946), Dummy Lynch (1948), Dwain Sloat (1949), Dutch Leonard (player and coach, 1949-56), Elmer Singleton (1957), Ed Mayer (1958), Marcelino Solis (1958), Charlie (Chick) King (1958-59), Irv Noren (1959-60), Danny Murphy (1960, 1962), Grady Hatton (player and coach, 1960), Jim McAnany (1961), Billy Cowan (1963-64), Don Landrum (1965), Ty Cline (1966), Adolfo Phillips (1966-69), Oscar Gamble (1969), Rick Bladt (1969), Boots Day (1970), Al Spangler (player & coach, 1970), Jose Ortiz (1971), Chris Ward (1972,1974), Mick Kelleher (1976-80), Scott Fletcher (1981-82), Wayne Nordhagen (1983), Thad Bosley (1983), Bobby Dernier (1984-87), Dave Meier (1988), Jerome Walton (1989-92), Eric Yelding (1993), Todd Haney (1994), Howard Johnson (1995), Bret Barberie 1996), Miguel Cairo (1997), Matt Mieske (1998), Chad Meyers (1999-2000), Corey Patterson (2001-05), Jae-Kuk Ryu (2006), Felix Pie (2007-08), Thomas Diamond (2010), Anthony Recker (2012), Brent Lillibridge (2013), Julio Borbon (2013), Justin Ruggiano (2014)
A bunch of has-beens, never-weres, almost-made-it guys and people you have probably never even heard of. Best known to you are likely Dernier, Walton and Patterson, young outfielders who it was hoped would have better careers than they did.
So let's talk about Mick Kelleher, who wore No. 20 for five seasons. Put mildly, Kelleher was a terrible hitter. In that era, though, middle infielders were for the most part not expected to be decent hitters; teams wanted solid defense and any bat they got was a bonus. Kelleher was a very good defensive shortstop and second baseman, never good enough to be a starter but a useful spare part.
On August 7, 1977, Mick started the second game of a doubleheader against the Padres. The Cubs had lost the first game 8-6, which dropped them out of first place for the first time since late May. They desperately needed a win to keep up any thoughts of playoffs.
In the top of the second inning, Steve Renko hit Dave Kingman with a pitch. The next hitter, George Hendrick, hit a ground ball to shortstop Ivan DeJesus, who flipped to Kelleher for the force play. Kingman slid in hard to break up the double play. It was then that the fun started.
Kelleher took exception to the hard slide and took Kingman down. This sort of thing does happen from time to time on a baseball field, but keep in mind that Kingman stood 6-6 and weighed 210, and Kelleher was listed as 5-9, 176 (and that was probably generous). Still, Little Mick held his ground. Both players were ejected; the Cubs won the game 9-4.
After his playing career Kelleher became a longtime coach and minor-league manager, including part of a year managing the Triple-A Iowa Cubs (he took over from Jim Essian when Essian was promoted to manage the big-league Cubs). Mick has a World Series ring -- he was the first-base coach for the Yankees from 2009 through last season.